At 11am on 17 May 1973, a hand grenade was thrown at Milan's police headquarters in Lombardy, Italy. It happened during a memorial ceremony there for police officer Luigi Calabresi, who had been shot dead in Milan a year earlier. Four civilians were killed by the blast and 45 other people were injured. The attacker was (30 April 1933 - 17 December 2000), who self-identified as an anarchist. He was arrested at the scene and in 1975 was convicted in relation to the attack and sentenced to life imprisonment.