The public prosecution department warned officials at Erasmus teaching hospital in Rotterdam that student Fouad L, who shot three people dead on Thursday, was showing signs of psychotic behaviour.

A letter from the department to the university authorities has been circulating in the Dutch media, and appears to have been published by L himself on a chat group on closed internet channel 4Chan.

In the letter, which Dutch News has seen, the department says that L was not only convicted of animal abuse, but that he showed other signs of disturbing behaviour, including lying on a pile of leaves in the garden half naked and screaming.

A search of his telephone had also turned up photographs of people who had been stabbed to death and of far-right symbolism.

According to the Telegraaf, the man was given a formal warning in 2018 for shooting at fish with a crossbow. Then in 2021, he was reported for throwing a rabbit against a tree. A search of his home, which was filthy and full of animal faeces also turned up two crossbows.

It is not clear when the letter was sent, but the department says it aim was to provide “support” to the university in “your role as the giver of diplomas and, if necessary, to take appropriate measures”.

The letter ends “I trust that the above information will assist you in your decision whether or not the person concerned qualifies for the basic medical diploma.”

Erasmus MC chairman Stefan Sleijfer told NOS on Friday morning that the shooter had been told he needed to undergo a psychological examination before he could be awarded his diploma.

“He had met all the formal criteria to be a doctor and had passed all his tests,” Sleijfer said. The exam committee “took the public prosecutor’s concerns seriously and decided a psychological check was needed.”

That process is still ongoing, he said.

The letter from the public prosecutor was placed on a 4chan chat group with the slug “political prosecution of Asperger men” in May. In the chat, someone who is thought to be L rants about being highly intelligent, considered weird by his fellow students and “becoming a raging alcoholic every time they suspend me”.

He talks about how he was convicted for torturing a rabbit because a “coalburner” videotaped him and says he does not connect with 99.9% of humans, whom he describes as “normies”.

He also states that the university had refused to give him his diploma and that he therefore lost his job and is destitute.

Three people died in Thursday’s shooting – a woman and her 14-year-old daughter, believed to be a neighbour of L, and a lecturer and family doctor who was shot dead at the hospital.