A knife attack at the Paris police headquarters on Thursday left at least four police employees dead and at least one police officer injured.
The attacker was shot dead by another officer. He killed one woman and three men in the attack. Three of them were police officers, one was a civilian employee.
The attacker was a technology administrator in the police intelligence unit. The French interior minister said he "had never shown any behavioral difficulties." French media reported he used a ceramic knife in the attack.
The incident occurred at the Ile de la Cite, the major island in the Seine in central Paris, at about 12:30 p.m. (1030 GMT).
Television pictures showed multiple emergency service vehicles at the location near Notre Dame Cathedral. The area was sealed off and the local metro station, Cite, closed.
Police did not immediately confirm details of the incident or the motive of the attacker, however investigators told reporters they are exploring the possibility of a personal conflict.
Investigators later confirmed they were working with anti-terror prosecutors, but that they were not yet convinced of a terror motive.
Police raided the attacker's home on Thursday afternoon and arrested his wife. She was not charged.
Paris Mayor Anne Hidalgo mourned the loss of the officers in a post on Twitter.
"Paris weeps for its own this afternoon after the horrific attack at the Police Prefecture," she wrote. "The toll is heavy: Several police officers have lost their lives."
Emery Siamandi, an employee at police headquarters, told The Associated Press news agency that he heard gunshots and immediately saw two officers leave an office weeping.
A third officer, who Siamandi described as the person who shot and killed the assailant, came out on his knees, also in tears.
French President Emmanuel Macron, Interior Minister Christophe Castaner, Prime Minister Edouard Philippe and the Paris prosecutor all attended the scene.
The incident happened a day after French police officers went on strike across the country to protest a growing mental health crisis in the force.
aw/msh (dpa, AP, Reuters)