Four police employees were killed in a knife attack at Paris police headquarters on Thursday, according to city prosecutor Remy Heitz.

The three policemen and a female police administrative worker were killed by a fellow member of staff, who was later shot dead, authorities told CNN.

The incident took place inside the building, which is located near Notre Dame Cathedral on the Île de la Cité in central Paris.

One victim is undergoing surgery, said French Interior Minister Christophe Castaner. He did not elaborate on the victim’s condition or injuries.

Castaner said the assailant was a 45-year-old man and had been an employee at the police station since 2003. There is no indication of a motive yet.

The island where the incident happened is on lockdown, with roads cordoned off by police and firemen, and ambulances on the scene.

The nearby Cité metro station was closed for security measures but has since been reopened.

Loïc Travers, Secretary of the National Police Alliance for the Ile-de-France region, told BFM TV that the attacker “has been with us for over 20 years.”

President Emanuel Macron is at the scene, accompanied by Prime Minister Edouard Philippe and Interior Minister Christophe Castaner.

The Elysée Palace said in a statement: “The President of the Republic went to the police station to show his support and solidarity to all the staff.”

Paris Mayor Anne Hidalgo said “several police officers have lost their lives” and that her thoughts are with the families of the victims.

She wrote on Twitter: “Paris cries for its own this afternoon after this terrible attack at the @prefpolice. Heavy casualties, several police officers lost their lives. On my behalf and that of Parisians, my first thoughts go to the families of the victims and their loved ones.

“During the Paris Council, we will pay tribute to the victims and will salute the unfailing commitment of police forces serving the security of Parisians. We know what we owe them,” she added.