French police is seen in front of the Paris Police headquarters in Paris, France, October 3, 2019. Photo: REUTERS/Christian Hartmann.

France’s anti-terrorism prosecutor said its investigation had detected signs of “latent radicalization” in the attacker who knifed four co-workers to death at the police headquarters in Paris this week.

The assailant, an IT worker at the headquarters, went on a rampage on Thursday, killing three police officers and an administrative worker, and wounding at least one other, before being shot dead by police.

Officials have not said there was a terrorism motive behind the attack, but handing a case to anti-terrorism prosecutors usually indicates a terrorism link is the focus of inquiries.

The anti-terrorism prosecutor, Francois Ricard, said his office had taken over the probe because of signs the crime was premeditated, of the attacker’s desire to die and of the nature of injuries found on at least one of the victims.

“The context of latent radicalization” and messages of exclusively religious character the attacker sent to his wife shortly before the crime were added factors, Ricard told a news conference.

The investigation also revealed contacts between the attacker and several individuals who are likely to belong to an Islamist Salafist movement, Ricard said.

The killer, 45, has been identified by officials only as Mickael H.

Ricard said that during a “deadly journey” the attacker first stabbed two police officers. A third police officer was killed in another office and an administrative worker died on the stairs.

The attacker was born on the French island of Martinique and had worked at the police headquarters for several years. He converted to Islam about 10 years ago, Ricard said.