The IT worker who stabbed four of his colleagues to death inside Paris’ police headquarters Thursday was a recent convert to Islam who had been acting erratically the night before the attack, reports say.

Le Parisien identified the attacker as Mickaël H., a 45-year-old computer maintenance specialist from Martinique who had worked at the police headquarters’ Intelligence Directorate unit since 2003. The Intelligence Directorate unit focuses on the fight against terrorism.

Mickaël H. had converted to Islam 18 months ago, but is not believed to have been radicalized, a police official told the Associated Press.

The attack Thursday, inside the building across the street from the Notre Dame Cathedral, left three police officers and an administrator dead, while a fifth person is being treated for injuries. Mickaël H., who was reportedly deaf, was gunned down by police.

Police officers control the perimeter outside the Paris police headquarters on Thursday after an administrator armed with a knife attacked officers inside. (AP)

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Investigators arrested the attacker’s wife Thursday afternoon at his home in Gonesse, a suburb outside of Paris where the pair married in 2014, according to Le Parisien. Information about possible charges was not immediately available.

Neighbors who spoke to the newspaper described the couple as being “very nice” and also “quiet,” mainly keeping to themselves.

But Mickaël H.’s wife told police Thursday that he was having visions and making incoherent statements the night before the attack, the Associated Press added, citing the television networks France Info and BFM TV.

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A masked police officer stands next to police tape following the knife attack Thursday. (AP)

The search for a motive in the attack is centering on Mickaël H.’s cellphone and computer records, as well as interviews with his widow and witnesses, the AP also reported.

The violence Thursday was not the first time police in Paris have been targeted in recent years.

In June 2017, a man who had been flagged by French investigators over ties to “the radical Islamist movement” deliberately rammed his car into a police van on the busy Champs-Elysees boulevard. He later died after his car burst into flames. No officers were reported injured in that incident.

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Two months earlier, a man armed with an AK-47 fired at a van full of officers on the same avenue, killing one and injuring two before being shot to death himself.

In June 2016, two French police officers were killed in front of their 3-year-old son at their home outside of Paris. That attack was said to have been carried out by a jihadist with a previous terrorism conviction, and ISIS claimed responsibility for it.