"On April 17, Klebold took a friend, Robyn Anderson, to the prom. Harris didn’t have a date but showed up at the after-prom party in the high school’s cafeteria. He played casino games with other members of the Trench Coat Mafia. He got angry.
"He was at the game where you throw baseballs at milk bottles and Eric picked up all three balls at once and threw them. He was getting really violent, shouting and stuff," Ungerland recalls. "The game coordinator told him to calm down. Eric got mad and walked away.""