(STMW) — A former Illinois state trooper was convicted of murder Thursday for fatally shooting his girlfriend at a graduation party in 2012.

A jury found 34-year-old Brian Himber guilty of first-degree murder for shooting and killing 29-year-old Tracy Mays in west suburban Westchester in July 2012, according to the Cook County state’s attorney’s office. He faces 45 years to life in prison for the crime.

Mays was sitting on a porch a few hours after she and Himber arrived at a graduation party when the off-duty trooper shot her multiple times with a .380 caliber gun, prosecutors said. He then shot himself once in the chin; he was off-duty at the time of the shooting, prosecutors say.

Mays was taken to an area hospital where she later died, prosecutors said.

Himber will be held in Cook County Jail until his sentencing hearing on March 4, the state’s attorney’s office said.

(Source: Sun-Times Media Wire © Chicago Sun-Times 2016. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)