PARIS - Four police employees have been killed in a knife attack at police headquarters in Paris.

The attacker, who was reported to be an employee of the police, was later shot dead by authorities. He killed three policeman and a female administrative worker. 

The incident took place on Thursday, at about 13:00 local time (6:00 AM CST) in the courtyard of the police building, which is located near Notre Dame Catherdral.

The area surrounding the crime scene, known as 'île de la Cité,' has been temporarily sealed off. An officer outside of the perimeter told reporters: “Île de la Cité is now a real island, no one can go and leave.”

The attacker's motive is currently unknown and an investigation into the incident is underway.