France’s anti-terrorism office will hold a news conference on Saturday after a policeman knifed four colleagues to death and hurt two more on Friday, raising questions about national security.

Axar.az reports citing Agence-France Presse that anti-terrorism prosecutor Jean-Francois Ricard will speak at 4 p.m. in Paris, his office said in a statement. An anti-terrorism probe was opened Friday evening after investigations suggested the attack may be a terrorist act. Initially, an interview of his wife by the police had suggested that the man may have had mental health issues.

The policeman was in charge of computer maintenance for French intelligence services and had access to secret data, Le Parisien reported on Saturday.

France’s anti-terrorism prosecutor recently said the threat of terrorism has returned in the country. A wave of attacks has shaken France since 2015, after assaults in the offices of satirical magazine Charlie Hebdo and a kosher grocery killed 17 people in Paris and then 130 at the Bataclan concert hall in the French capital.