Counter-terrorist investigators have taken over the probe into the stabbing rampage at Paris police headquarters, which saw a police computer expert with 15 years on the force allegedly murder four and injure two, sources say.

While the French government has not officially confirmed terrorism was the motive in the deadly stabbing attack, a judicial source close to the investigation told AFP the anti-terrorism prosecutor took over the case on Friday after police interviewed close associates of the 45-year-old perpetrator, Mickael Harpon, and examined his cellphone.

Also on rt.com Stabbing attack at Paris police HQ: What is known

Harpon reportedly converted to Islam about 18 months ago, but the government has gone out of its way to remind the public that “converting to Islam is not an automatic sign of radicalization.” An initial search of the house he shared with his wife and children in a low-income suburb near the Paris airport yielded no indication he had acted out of radical religious motives, and his wife claims he “heard voices” the night before murdering his four colleagues.

READ MORE: Paris police knifeman ‘heard voices’ before deadly rampage

Co-workers expressed shock that Harpon, who was shot dead by police responding to the attack, was behind the rampage, noting that he had “never shown any behavioral problems” or caused any trouble since joining the force in 2003.

Also on rt.com Crumbling blue line: Overworked, demoralized French police stretched to breaking point

Like this story? Share it with a friend!