Policemen stand near a vehicle on the place du Trocadero in Paris on April 21, 2017.Bertrand Guay | AFP | Getty ImagesAn administration worker with Paris police killed four people in a knife attack at the force’s headquarters in central Paris on Thursday before he was shot dead by an officer, police officials said.The assailant’s motive was not immediately clear. The attack took place in the heart of the French capital, near to the Notre-Dame de Paris cathedral.The area around the police headquarters was sealed off and the nearest metro station was shut for security reasons, the transport authority said.”We do not know his motives, we do not know why this colleague has done this,” Loic Travers, local head of the Alliance police union, told BFM TV. One person was initially reported dead and two police sources said later that the death toll had risen to four, not including the attacker.”The person behind the attack has been shot (dead) by another colleague,” Travers said. President Emmanuel Macron is to visit the headquarters and Prime Minister Edouard Philippe and Interior Minister Philippe Castaner are at the site. A police spokesman said he had no comment on the incident. An official at the Paris prosecutor’s office said its anti-terrorist unit had not yet been called upon to investigate.