A staffer at Paris police headquarters who stabbed four colleagues to death on Thursday adhered to "a radical vision of Islam", an anti-terror prosecutor said Saturday, according to AFP.
The 45-year-old computer expert had been in contact with members of Salafism, an ultra-conservative branch of Sunni Islam, and defended "atrocities committed in the name of that religion", Jean-Francois Ricard was quoted as having told reporters.
Three police officers and an administrative worker -- three men and one woman -- died in the lunchtime attack on Thursday at the police headquarters.
The assailant, named as Mickael Harpon, was shot dead by a policeman, who was a trainee at the police headquarters.
Harpon, born on the French overseas territory of Martinique in the Caribbean, converted to Islam about 10 years ago, the prosecutor said. He had no police record but was investigated for domestic violence in 2009.
Sources said he had worked in a section of the police service dedicated to collecting information on jihadist radicalization.
Harpon held a high-level "defense secrets" security clearance, which authorized him to handle sensitive information of national defense importance and would have subjected him to regular, stringent security checks.
On the morning of the attack, Harpon bought two knives -- a 33-centimeter long kitchen knife and an oyster knife -- which he kept hidden, Ricard said.
He showed "absolutely no signs of nervousness" as he circled back to police headquarters, according to CCTV footage examined by police, the prosecutor said.
The attack, from his return to the office, the killings and his death by police bullets, lasted seven minutes, Ricard said.
On Friday, French detectives referred the investigation into the knife rampage to anti-terrorist prosecutors.
Ricard said on Saturday that Harpon exchanged 33 text messages with his wife shortly before the attack.
The messages exclusively concerned religion, and the attacker ended the conversation with "Allahu Akbar" and told her to "follow our beloved prophet Mohammed and meditate on the Koran", according to the prosecutor.
The wife was being held by police on Saturday.
France has been hit by a wave of terrorist attacks in recent years, beginning with the 2015 attack on the offices of the Charlie Hebdo satirical magazine which was followed by the attack on the Hyper Cacher kosher supermarket in which four people were murdered.
Since those attacks, France has been hit by a number of attacks claimed by the Islamic State (ISIS), the biggest one being the attack in November of 2015 in which 129 people were murdered.
The country has been under a heightened alert in recent years in the wake of the attacks.