A Paris police tech worker has gone on a rampage in the French capital, killing four of his colleagues before being shot dead.

Forty-five year old Mickael Harpon worked for two decades in the IT department of the intelligence section at the French police's Paris headquarters. He reportedly worked in the division responsible for collecting information on terrorism and radicalisations.

Last Thursday night Australian time, French prosecutor Jean-Francois Ricard said Harpon stabbed three people inside two offices at the police headquarters, and then attacked two women in a stairway before being shot and killed by a trainee policeman in the courtyard, just metres from the Notre Dame Cathedral.

The three men and one of the women died from the wounds inflicted, while the other woman is being treated in hospital.

While it was initially believed the attack was linked to an internal workplace feud, the case has now been turned over to anti-terror investigators, based on text messages Harpon sent to his wife before his rampage and other information later found by police.

The attacker’s home in Gonesse, a working class suburb north of Paris, was searched on the same day. His wife was taken into custody but not charged.

Harpon reportedly converted to Islam about 10 years ago, and did not have a police record. As part of his IT work, he would have the high-level “defence secrets” security clearance, which authorised him to handle extremely sensitive information on national security.

He joined the police force in 2003 and worked as a computer expert.

The attacker is said to have sent more than 30 text messages to his wife in the lead-up to the attack.

“These SMS, if not explicit about any possible attack, nevertheless were sent only 30 minutes before the knives were bought,” Ricard said.

Harpon bought the two knives used the attack earlier on the day of the attack, and in CCTV footage showed “absolutely no signs of nervousness”, Ricard said.

The case has been given to the anti-terrorism division due to the “premeditated character of the attack, his professed desire to die during the attack, the nature of the attacks and the injuries inflicted on at least one of the victims, the content of latent radlications and the exclusively religious message sent before the attack”.

Paris Mayor Anne Hidalgo and President Emmanuel Macron attended the scene on Friday.

“Paris weeps for its own this afternoon after this terrifying attack in the police headquarters,” Hidalgo said. “The toll is heavy, several officers lost their lives.”

Macron said the incident was a “veritable tragedy”, and the president will be leading tributes to the four victims on Tuesday, Paris time.

The three male police officer victims were from the anti-terrorist department, while the female employee was from the human resources department.

The incident took place just days after thousands of French police officers marched in Paris to protest against low wages, long hours and increasing rates of suicide in the police force.

If you or someone you know needs help, contact Lifeline on 13 11 14 , Beyond Blue on 1300 224 636 or the Suicide Call Back Service 1300 659 467.