The wife of the French IT worker who fatally stabbed four of his co-workers at Paris police headquarters has told investigators her husband heard voices in his head the night before the attack, a source close to the investigation said.
The 45-year-old worker went on a rampage at the headquarters where he worked at lunchtime on Thursday, killing three police officers and an administrative worker, and wounding at least one other, before he was shot dead by an officer.
French media reported that the attacker had converted to Islam 18 months ago. Officials have not said anything about a possible motive for the attack and said they were still trying to discover if there was a terrorism link.
"No hypothesis is being ruled out at this stage," Paris police chief Didier Lallement said at a news conference on Friday.
The attack took place on the historic Ile de la Cite island in the River Seine, close to Notre-Dame de Paris cathedral. The area was locked down after that attack, with armed security personnel in camouflage gear patrolling a bridge over the river.
The attacker's wife was on Thursday taken into police custody, but not charged. During interviews with police, she described how her husband had heard voices on Wednesday night, according to the source close to the investigation.
A second source informed about the investigation said the attacker was believed to have had an "attack of insanity" that led him to carry out the attack.
The killer, identified by sources close to the investigation as Mickael H., had worked at the police headquarters for several years and had given no cause for concern about his behaviour, officials said.
In the past four years, the French capital has been rocked by violent attacks resulting in mass casualties.
Co-ordinated bombings and shootings by Islamist militants in November 2015, at the Bataclan theatre and other locations around Paris, killed 130 people in the deadliest attacks in France since World War Two.
The knife attack unfolded just after midday on Thursday when the attacker, on the first floor of the police headquarters, used a kitchen knife to stab three male police officers, before taking the stairs down to the ground floor of the building.
On the staircase he came across two women staff, according to Le Parisien newspaper, which cited an internal police report on the incident. He stabbed both of them, fatally wounding one.
He then moved out into the courtyard of the police headquarters. There, according to the Parisien account, a police officer responsible for security at the building, after issuing warnings, fired several shots at the attacker, including to his head, and killed him.
The officer used a Heckler & Koch G-36 assault rifle, the newspaper reported.
The police officer who halted the attack had recently completed his training and had been in the job for only six days, Lallement, the police chief, told reporters.