A former Illinois state trooper was convicted Thursday of killing his girlfriend while the two were attending a graduation party in Westchester in 2012, prosecutors said.



Brian Himber, 34, of Chicago, was convicted of first-degree murder for the July 22, 2012, fatal shooting of Tracy Mays, 29, according to Cook County prosecutors.



At the time of the shooting, Himber was off duty from his job as a state police trooper and was with Mays when they attended a graduation party in Westchester, according to a news release from Cook County State's Attorney Anita Alvarez.



While at the party, Himber fired a .380-caliber handgun and shot Mays several times as she sat on a porch, prosecutors said. Mays, who was a Joliet resident, was taken to a hospital, where she was later pronounced dead.



After the shooting, Himber tried to kill himself, police said, leaving him with critical injuries.