The wife of the French Police employee who killed four colleagues at the Paris Force’s Headquarters on Thursday says he had a psychotic episode, was incoherent and heard voices the night before.

The 45-year-old Michael Harpon was shot dead by Police at the scene of the attack. French officials are trying to establish the motive behind the killings. Although Harpon’s wife has been taken into custody, the Paris prosecutor’s office says she has not yet been charged.

The woman has apparently told the French Police that Harpon, whom she described as being 70% deaf had a disagreement with his bosses and felt that his work was unappreciated, prompting Police union officials to suggest that he may have been involved in a workplace dispute.

At about 13:00 local time, Harpon was reported to have gone into the building and straight to his office where he began attacking colleagues with a knife.

He stabbed three people inside two offices and two women on a stairway, before he was shot dead by an officer inside the building’s courtyard. Paris prosecutor Rémy Heitz told reporters that three men and one woman were killed.

A fifth person, who was critically injured in the attack has been transported to an hospital for surgery.

President Emmanuel Macron, Prime Minister Edouard Philippe and Interior Minister Christophe Castaner have all visited the site.

According to Castaner, Harpon was a 45-year-old Information Technology specialist who had worked in the intelligence division of the Paris Police force for 16 years.

Mr. Castaner added that there had been no warning signs about the attacker as he ‘looked a model employee’.

According to reports, Harpon converted to Islam 18 months ago and had recently stopped talking to female colleagues in the office. A government spokeswoman however said there was no indication he had been radicalized before the attack.

The attack followed a rare nationwide police strike on Wednesday, which saw thousands of officers demonstrating in Paris over working hours, shortages in resources and controversial pension reforms.