Most, if not all, of Freud's musings, as well as his so-called theories, are based on real event from his life. Remarkably, no one had taken his seriously when he wrote about murder. And there's lots of dead people in Freud's life, many of them not even middle-aged. As Freud explained in his dream book - suffering from pathological ambition - to promote his career - he wanted his professional competitors dead.
For most "normal" people, a step from wishing someone dead to the deed is quite big. For a psychopathic character like Freud, it was not. Just imagine a person, who believes that he is cleverer than the rest, most certainly cleverer than the police, killing with impunity to advance his career. Could this have been Freud?
Freud's problem, as a master murderer, was obvious. As so many other serial killers who remained at large even though killing multiple victims for years, Freud craved recognition and fame. At the same time, he realised that should people learn about his lethal deeds, he wouldn't remain at large for long. So what could he do?
One way of telling stories about himself was to pretend he was recounting dreams when revealing his own criminality. Another way was to claim that he was recounting someone else's criminal deeds.
One such murderous case is the story of a mysterious poisoner, Mr H. And who could that poisoner be if not ... the infamous Dr Freud, who brazenly recounted the whole story in one of his works, even hinting at the identity of the victim.
For over a century, for all people - with a couple of remarkable exceptions - Freud's murderous deeds remained unknown. No one took him seriously, and for obvious reasons. Most people say nasty things they don't mean, from time to time, especially when they are very upset. The difference was that Freud meant every word he said and acted upon them. And, who could suspect a learned professor of being a ruthless serial killer?

This is Freud's "confession", verbatim, as it appeared in the Lecture IV on Parapraxes (Slips of the Tongue) of 1915-1917. Just imagine how brazen one needs to be to openly reveal one's own murderous deeds to a crowd of listeners:

Obtaining pathogens

You may perhaps remember the case of a murderer, H., who found the means of obtaining cultures of highly dangerous pathogenic organisms from scientific institutes by representing himself as a bacteriologist. He then used these cultures for the purpose of getting rid of his near connections by this most modern of methods.

Freud's experiments on men

Now on one occasion this man complained to the Directors of one of these institutes that the cultures that had been sent to him were ineffective; but he made a slip of the pen, and instead of writing ‘in my experiments on mice or guinea-pigs’ he wrote quite clearly ‘in my experiments on men’.

Circumstantial evidence

The doctors at the institute were struck by the slip, but, so far as I know, drew no conclusions from it. Well, what do you think? Should not the doctors, on the contrary, have taken the slip of the pen as a confession and started an investigation which would have put an early stop to the murderer’s activities?
... a slip of the pen like this would certainly have seemed to me most suspicious; [it] was certainly a piece of circumstantial evidence; but it was not enough in itself to start an investigation. *
* SE 15, pp. 69-70.