Investigators combed an IT staffer's computer Friday for clues to his motive for stabbing four colleagues to death at police headquarters in Paris, as his wife said he had been "agitated" before going on the rampage with a kitchen knife.
The 45-year-old computer expert killed three men and a woman -- three police members and an administrative worker -- in a frenzied 30-minute attack that ended when he was shot in the head.
Two others were injured in the Thursday lunchtime stabbing spree that sent shock waves through an embattled French police force already complaining of low morale.
Officials said there was no indication that the rampage was an act of terror but emphasized no theory was being ruled out at this stage.
The man, who was born on the French overseas territory of Martinique in the Caribbean and was a recent convert to Islam, had worked for the police for over a decade-and-a-half without ever arousing suspicion.
- 'Not automatic sign' -
The attacker's wife told investigators her husband, who had a severe hearing disability, displayed "unusual and agitated behavior" the night before his crime, a source close to the investigation told AFP.
A search of the couple's house in a low-income Paris suburb near Charles de Gaulle airport yielded no evidence that the man, who became a Muslim about 18 months ago, had been motivated by radical religious ideology, the source added.
Computer equipment seized in the search was still being examined. AFP correspondents saw investigators -- faces concealed by balaclavas -- lead out from the house late Thursday a man and a woman who hid behind hoods.
The possibility of a terror motive "has clearly not been ruled out," government spokeswoman Sibeth Ndiaye told Franceinfo radio on Friday.
"But it is important to emphasize -- you are not a terrorist because you are Muslim and converting to Islam is not an automatic sign of radicalization. The facts need to be looked at carefully" she said.
"We do not have any indication that the perpetrator was radicalized."
One motive investigative sources mooted was a personal conflict at work.
The man was employed as a computer scientist in the intelligence branch at police headquarters, a stone's throw from the Notre-Dame cathedral in the historic heart of Paris.
He had worked for police since 2003 before committing the deadliest attack on police in France in years.
Shortly after the killings, Paris prosecutor Remy Heitz said anti-terror investigators were not involved in the murder probe.
- A 'quiet person' -
"He was a very quiet person. I used to see him going to the mosque but he practized (his religion) in a normal way," a neighbor, who asked not to be named, told AFP.
Locals said the man had two children aged three and nine.
Interior Minister Christophe Castaner said Thursday the assailant had "never shown any behavioral problems" and never aroused the "slightest reason for alarm".
The man used a kitchen knife to stab two policemen and a male administrative colleague in two offices on the first floor of the building, before attacking two women on the staircase on his way to the courtyard outside.
One was a police officer who died at the scene. The other, an administrative worker, was seriously injured.
The assailant wounded another policeman in the courtyard before he was shot dead by a colleague, sources told AFP.
The lives of the two injured colleagues are not in danger, a source said Friday.
Tension has been growing in police ranks, stretched to the limit after months of weekly "yellow vest" anti-government demonstrations and years of high alert following a string of terror attacks in France.
"The police are a big family and the fact that police headquarters were hit like this is something that is pretty traumatic," said a spokeswoman for the force, Laetitia Vallar.
"Yesterday we put in place a psychological help unit for all those in need," she told BFM-TV.
Thousands of police officers marched in Paris on Wednesday for better working conditions, a rare protest that took place against the backdrop of a spike in police suicides -- 52 so far this year.
The police have also been a recurring target of jihadist groups, such as Islamic State, behind a wave of attacks since 2015 -- from large synchronized assaults to isolated knife and gun attacks.