According to a neighbor, a lady shot by a man suspected of killing three people in Rotterdam had often complained to police about him.
Prosecutors were also aware of Fouad L and had alerted the hospital where another victim was shot, according to an email.
The hospital was informed that Fouad L, 32, had displayed “psychotic behavior.”
On Thursday, he was detained after reportedly shooting his neighbor and her kid, as well as a professor at the Erasmus Medical Center.
The Dutch authorities have not revealed any specifics regarding a probable motivation, but they have stated that the victims were most likely purposely targeted.
Roy, who lives in the same apartment block, told the BBC the family lived next door to Fouad L and had repeatedly reported him to the police.
“Once he threw a dead rabbit into their garden,” the 20-year-old said.
The police would come, Roy added, but “he always had the curtains closed and never opened the door”.
“They had so many chances to kick him out. This is social housing, he should have been evicted a long time ago,” he said.
The email – sent by the Dutch public prosecution service to the teaching hospital where Fouad L studied – described his previous “worrying behaviour”, including him being found “half-naked in the garden on a pile of leaves”.
In the message, prosecutors suggested his behaviour could affect whether the hospital would grant him a medical diploma.
The suspected gunman posted the email in a web forum himself and complained about teachers “sabotaging” him.
He described himself as an alcoholic and said he had been fired because he was unable to finish his medical degree.
Prosecutors have confirmed the authenticity of the email, Dutch public broadcaster NOS reports.
Erasmus Medical Center chairman Stefan Sleijfer said in a statement that the prosecutor’s warning had been taken seriously.
Fouad L was told to undergo psychological evaluation and was denied a doctor’s licence unless a psychologist declared him fit to practise medicine, Mr Sleijfer said.
During a search of his phone at the time of the animal cruelty investigation, prosecutors also found pictures of people being stabbed as well as right-wing extremist images.
Fouad L set fire to the residential building after shooting the woman and her daughter, police said. Emergency services took the daughter, 14, to hospital but she later died from her injuries.
Bouquets of roses and sunflowers have been attached to the black screen placed by police around the crime scene.