When he got enraged, he beat people to death. Because of his behavior, the mafia approached him, and he worked for them as a contract hit man for many years.
One of the reasons the mafia chosen him was his ability to kill a random, and innocent target without remorse. When he was captured and imprisoned, he gave many interviews to psychiatrists and TV programs, where he worked to try and understand why he had so much enjoyed hunting people down and killing them.
He earned his nickname Ice Man, because he often froze the bodies of his targets in order to prevent information on time of death to be used against him.