Freud’s parasitic character is apparent from his fantasies about how to become rich, without having to work for the money. Thus, during his stay in Paris in 1885-1886, having met a well-to-do Austrian physician, Richetti, and his wife, Freud fantasised how he could come into a possession of their money. This is what his biographer, Jones, had to say about it, The Richettis were evidently fond of Freud and since they had no children, he was able to indulge in what he calls Schnorrer [beggar] phantasies about inheriting some of their wealth.*
As a matter of course, for Freud to inherit their money, they would have to be dead first. Luckily for them, in their case, Freud didn’t act on his fantasy.
Freud’s schnorrer **fantasies didn’t stop on his return to Vienna. This time it was a fellow doctor, Nathan Weiss’ wealth, that Freud was planning to inherit.
* Jones, Sigmund Freud: Life and Work: The Formative Years and the Great Discoveries, 1856-1900. (1953, p. 188)
** Schnorrer is a Yiddish pejorative term for a beggar who presents himself as respectable and feels entitled to the alms received, Just like Freud.

Nathan Weiss was a lecturer in neurology at the University of Vienna, who, allegedly, committed suicide. Notably, after his death, and thus profiting from it, Freud replaced him in this position. Together with Freud, Weiss worked at the Vienna General Hospital, where in 1883, at the age of 32, in the year he died, Weiss was appointed head of the outpatient clinic. As a matter of course, Freud wasn’t happy that he wasn’t promoted to the role rather than Weiss. Freud, as he revealed in the dream book, was pathologically ambitious, sacrificing to his ambition the very people he loved. What kind of sacrificing Freud had in mind is a good question.

On a Sunday, September 16, 1883, three days after Nathan’s death, having returned from his funeral, Freud penned the longest letter he ever wrote to his fiancé. (1)
Remarkably, it was not a love letter, but a letter about the death of his “friend”. Apparently, taking into account the length of the letter, this particular death had some special significance for Freud. In the letter, Freud informed his fiancé about his, deeply shattered emotional condition, due to the fact that he, just returned from the funeral of my friend Nathan Weiss.      
        Even though Freud called Nathan his friend, besides the latter being mentioned in a couple of letters to Martha (of September 16, 1883, and of January 10, 1884, (2) there’s not a single mention of Nathan anywhere in Freud’s letters, papers or books. But, of course, having worked in the same General Hospital as Weiss, Freud knew Nathan. In his letter to Martha of October 5, 1882, Freud told her that he was, serving as an Aspirant in the General Hospital. (3)
        Actually, being Freud friend was a dangerous business. Several of his “friends”, Schönberg (his love rival), Paneth (who replaced Freud in the institute) and Fleischl (Freud’s superior), died under suspicious circumstances, sacrificed to Freud’s “pathological ambition”. (4)
As Freud revealed in his dream book, he was sacrificing to my ambition people whom I greatly value. (5)
What his sacrifice entailed, taking into account, that they were all dead, is not hard to guess. Also, Nathan was included in this number, a dangerous distinction.
(1) Freud, Sigmund, The Letters of Sigmund Freud, (1960, pp. 58-66).
(2) Freud, (1960, p. 88).

(3) Freud, (1960, p. 30).

(4) SE 4, p. 192.

(5) SE 5. p. 422.

In his PhD thesis of 2013, Michael Jacobs, observantly, pointed out that Freud’s description, of the events leading to Nathan’s death, basically replicated / plagiarised the plot, and personas, of A Midsummer Night’s Dream by Shakespeare. This is how Jacobs summarised the tragic story as recounted by Freud:
Weiss was in love with a young woman who rejected him - but he persisted in wooing her with presents and money until she could no longer refuse him. Before the wedding, however, she asked him to marry her sister (as Hermia might have wished Demetrius to marry Helena) and the marriage was postponed.
Without doubt, nothing of the Weiss' tragic love story was true. As it is apparent, in his letter, Freud plagiarised Shakespeare’s play. In fact, it is doubtful that he knew anything about Weiss' romance. This is how Jacobs summarised Freud's plot:
Her family (like Egeus) persisted in their pressure on the young woman, and eventually she gave in, but within four days of the couple’s return from their honeymoon Weiss hanged himself. (1)
Freud's life-long interest in Shakespeare is an obvious case in point. As his biographer, Ernest Jones, reported:
Shakespeare in particular … he read over and over again and was always ready with an apt quotation from his plays. (2)
In fact, Shakespeare was one of, The three great men ... with whom he perhaps partly identified himself. (3)
Apparently imagining himself a new Shakespeare, Freud built the whole fake tragic love story around Nathan’s death.
As so often in his writings, also in this case, Freud used his own autobiographical details to embellish this story, and some did notice. 
Hence, in her book, Mourning Freud, Madelon Sprengnether, a literary scholar, pointed out that,
Nathan's death, in Freud's view, is the direct result of his unfortunate marriage. In almost a parody of Freud himself, he insisted on courting a woman who was cold toward him.
Without doubt, she is right in noting that Freud's description of Nathan's wife is a carbon copy of Freud's own fiancé. As Sprengnether pointed out,
these are all concerns ... that surface at one time or another in Freud's correspondence with Martha. (4)
Thus, Freud not only used the Shakespeare’s plot in the Nathan’s fictional tragic love story, but also, for a good measure, inserted elements from his own relationship.
Taking into account Freud’s Shakespearean literary theft, it is apparent that most of the story, if not all, as told by Freud in the letter – how would Freud know all the details of Nathan’s romance?  - is a falsehood intended by Freud to provide a believable motive for Nathan’s suicide. But, why would he feel the need to do that?

This is how Freud recounted Nathan’s death: On the thirteenth [a Thursday], at 2 p.m., he hanged himself in a public bath in the Landstrasse.
Not unexpectedly, Freud asked an important question that, assuming it was a suicide, no one else, but Nathan himself, could have known the answer to, What drove him to it?
Nathan's suicide begs a number of questions. What was he doing in a public bathhouse, at that hour, when he should have been at work at the hospital? And why would he choose a bathhouse for the suicide?
Most certainly, as a man of substantial means, Weiss didn't need to visit a public bathhouse to have a bath.
Just as nowadays, at the time, Vienna had its fair share of gay bathhouses, not only intended for bathing but, also for homosexual activities. The one in Landstrasse, near the centre of Vienna, where Weiss died, doesn’t exist anymore, but another such establishment is the Central Bathhouse, which opened a few years after Nathan’s death, in 1889. In fact,
the Zentralbad in Weihburggasse … has remained as a meeting point for homosexuals to this day.*
Would Nathan.a newly married man, be engaging in homosexual activities on the side? Were Weiss and Freud lovers?
A case in point. The distance, between the Vienna General Hospital, where Weiss worked, situated at Währinger Gürtel 18-20, and the bathhouse where he died is approximately 6 km, thus more than a walking distance. Even assuming that he would have taken a cab, the visit to the bathhouse would have taken a significant amount of time. Most certainly, Nathan wasn't having a bath. So, was he having a date with a gay lover?
* Central Bathouse, Vienna, https://en.wikipedia.org/wiki/Central_Bathhouse_Vienna, (July 18, 2022)

Freud claimed that Nathan, left two letters, one to the police asking them to inform his parents tactfully and to suppress any word of it in the newspapers, the other to his wife.
This statement is baffling. How could Freud have known that Nathan left suicide letters at all, and how many, and to whom they were addressed? How, only three days after Nathan’s suicide, could he have known what was in the letter to the police? Without doubt, the police would not reveal the content of the suicidal letter to an outsider like Freud. And, since the letter asked the police not to provide any information to the newspapers, it wouldn’t have been published.
Thus, Freud could only have known about the existence, and content, of the letter to the police, if he either wrote it himself, was present when Nathan wrote the letters, or if he invented the alleged letter and its content. Considering that most, if not all, of Freud’s story is fiction, unless Freud murdered Nathan in the bathhouse, the last option seems the most feasible.

Further, Freud claimed that, By Thursday evening [thus, on the same day] the news [about Nathan’s suicide] was already known in the hospital. This claim poses yet another question. How could Nathan’s death, already in the evening of the day of his suicide, be known at his workplace?
Besides the police, only the people who found him, and the ambulance personnel, knew about Nathan’s death. Unless he was a frequent visitor to the bathhouse, which is unlikely, the bathhouse personnel wouldn't have known who Nathan was, and where he worked.
So, who else could have already, on the same day, notified the hospital about Nathan’s demise? And if Freud is telling the truth, there's only one person that could have spread this kind of information, the murderer, somehow connected to the hospital in which Nathan worked. Freud claimed that, His [Nathan's] brother, Sekundararzt [doctor] in the hospital, confirmed the news [of Nathan’s death].
So, it wasn't the brother that was the source of the gossip at the hospital. But, then, who was it? Freud?
Of course, Freud, the fiction writer, could have been lying also about the whole hospital gossip story. 

Having allegedly returned from Nathan’s funeral. this is how Freud recounted what, according to him, went on.
Over his corpse began the feud of the families and on his still open grave there sounded a loud discordant scream for revenge, as unfair and as reckless as if he had uttered it himself.
There’s little doubt that Freud lied about what happened. In fact, it is unimaginable that the families of the deceased and the wife’s would be demanding a revenge for Nathan’s death at the funeral. Notably, writing about this sombre occasion, Freud denigrated not only the families, but also the dead man, claiming that the families’ “screams” were as “unfair” and “reckless”, as if it was Nathan who had uttered them!
As Freud recounted, a relative of Nathan’s family, delivered the eulogy quoting from the Bible. This is Freud’s version of what happened:
The lecturer Friedmann, a relation and colleague of his old father, began: “Thy name was Noah, and thy parents associate with it the dictum: "Thou shalt be the comfort and the support of our old age." And all this comfort now lies here. If a corpse be found, and one does not know by whose hand he died, then one must turn to the next of kin; they are the murderers. But we, his parents and brothers, have not shed his blood.
Further, and bizarrely, Freud claimed that,
in clear words he [the speaker] began to accuse the other family [the wife’s] of having dealt the fatal blow.  And all this he spoke with the powerful voice of the fanatic, with the ardor of the savage, merciless Jew.
If this is truly what happened, the situation was out of the ordinary. No wonder that, as Freud explained,
We were all petrified with horror and shame in the presence of the Christians who were among us. It seemed as though we had given them reason to believe that we worship the God of Revenge, not the God of Love. Pfungen’s thin voice was lost in the reverberation of the wild accusation of the Jew.
Reading Freud’s description of the incident, it is hard to believe that Freud recounted a real event rather than a figment of his lunatic mind. After all, we have only Freud’s words to rely upon, and they aren’t reliable at all. But maybe an analysis of the biblical quote can provide a clue as to what really said.
As one would expect from a pathological liar, the original passage in the Bible differs significantly from the one recounted by Freud. It says:
If a dead body is found ... your leaders and judges are to go out and measure the distance from the body to the nearest cities. The leaders and judges of the city that is nearest the corpse will then take a heifer … and there break the neck of the heifer. The Levitical priests will then step up. God has chosen them to serve him ... by settling ... violent crimes ... Finally, all the leaders of that town that is nearest the body will wash their hands over the heifer … and say, “We didn’t kill this man and we didn’t see who did it. ... O God. Clear your people Israel from any guilt in this murder.*
Thus, even though the alleged eulogy was based on the biblical one, it had very little to do with it. Rather it was totally distorted, a lie, and it is apparent by whom. As a matter of course, it is highly unlikely that the person delivering the eulogy - in front of the rabbi, and Nathan’s father who was a Talmudic scholar - would have manipulated the quote to this very extent. Without doubt, it was Freud who manipulated the quote, turning it into a bizarre, hateful accusation, allegedly pronounced over the dead Nathan's grave.
As one recent biographer revealed, it was,
Isaac Weiss's [Nathan’s father’s] colleague, Meir Friedmann (1831-1908), also a lecturer at the Vienna Beth Ham Idrash and a great Talmud scholar, [who] quoting the Old Testament, that openly called for revenge.**
Taking into account the position of the person delivering the eulogy, and the fact that he was a colleague of Nathan’s father, it should be obvious that a respectable Talmud scholar would never, in this bizarre way, have distorted a Biblical quote. But people are easily fooled, as Freud was aware of.
Freud further recounted the fact that, Both his widow and his father have issued special mourning announcements, which further contradicts Freud's claim about the families' quarrel at the grave.
* Deuteronomy 21.
** Wistrich, Robert S., The Jews of Vienna in the Age of Franz Joseph, 2019, p.557.

Nathan was found hanging in his cabin by the attendants. Assuming that it wasn't a suicide, there's a question, if he was killed by someone, how was it done?  Both men would have been inside the cabin. It is not easy to overwhelm someone who fights back. Most certainly, if there was a struggle, someone would have heard it. And there would be signs of a struggle inside the cabin, but, apparently, there weren't any,
Maybe, when Nathan turned his back to him, the killer hit him on the head rendering him unconscious, and then hanged him then? Or maybe, the doctor killer, injected him with some sleep-inducing or paralysing drug and then hanged him?
And what about the letters? Would the killer have brought letters with him or written them once Nathan was killed? It isn't easy to falsify someone's writing style.
Most suicides are being committed at home. So why would Nathan have chosen a bathhouse for his suicide? And the answer is obvious. He didn't want to upset his wife. And why not at the hospital? Maybe he didn't want his colleagues to see him dead. I guess, even though going to hang himself, Nathan gave lots of thought about the choice of the "venue", and about who would find him. After all, no one knew him at the bathhouse.
The shock he gave the attendants was collateral damage that goes with the job, or so he may have thought. If you think about it, there aren't many places suitable for a suicide by hanging. What is odd is the fact that he didn't chose to poison himself. After all, as a doctor, he had access to ready access to drugs in the hospital pharmacy. But it is mostly females that use drugs to kill themselves, while death by hanging is the most common form of suicide for men,
So maybe, after all, Weiss killed himself. He wouldn't be the first, nor the last. But why?
Actuallly, Freud's deranged explanations of Nathan's motives tell us more about Freud than about Nathan.
So why did Nathan, so shortly after his return from the honeymoon, commit suicide?