A man armed with a knife attacked officers inside Paris police headquarters, killing at least four, before he was fatally shot Thursday, a French police union official said. It wasn’t immediately clear how far the assailant got inside the building, which is located across the street from Notre Dame Cathedral.

Police union official Loic Travers said four police officers suffered fatal wounds and the attacker was shot “in a situation that appears to be self-defense.” The motives of the midday attack were not known.

Another police union official, Jean-Marc Bailleul, told French broadcaster BFM TV that information was still coming in but he understood the attacker was a police department employee. The attack came a day after thousands of officers marched in Paris to protest low wages, long hours and increasing suicides in their ranks. (Agency report)