The four victims - three men and one woman - were honored on Friday with a silent minute outside the police headquarters in central Paris. Among the audience were, among others, the French Minister of the Interior Christophe Castaner.

A little more than a day earlier, a 45-year-old man, who had an IT service at the police headquarters, had killed four people with a large kitchen knife inside the building.

Anti-terror investigation

The motive for the act is still unknown, but on Friday afternoon the case was taken over by anti-terror prosecutors, several French media writes. According to Le Parisien, at least one of the victims must have had his throat cut.

The first three victims were killed in connection with the offender's office. All were men, two police officers and one person with an administrative service. Thereafter, the 45-year-old will continue to a flight of stairs where he killed a female police officer and seriously injured a female HR employee, reports Franceinfo.

The man was then shot to death by a young police officer who had only worked six days at his new job.

"Heard voices"

The wife of the 45-year-old has in interrogation stated that her husband behaved strangely and "heard voices" the night before the act. French media has reported that he had converted to Islam 18 months earlier but that he was not reported to have shown any signs of radicalization.

A spokesman for the French government said earlier Friday that the incident is being investigated as a murder and not as terrorism.

Later in the afternoon, however, the case was taken over by the prosecutor's office investigating terror crimes, according to several French media. Franceinfo refers to sources that state that it is due to "new evidence that has emerged in the investigation" without specifying further.