On the morning of September 1, 2013, 32-year-old Sergeant Derek Ray Johnson stopped to check a vehicle that was parked oddly on a quiet street in Draper, Utah. Before he could exit his patrol car he was struck by gunfire. Mortally wounded, Sgt. Johnson radioed for help and was taken to Intermountain Medical Center, where he died. He is survived by a wife and son.

Police focused on the two people in the vehicle, Timothy Troy Walker and his girlfriend, Traci Vaillancourt. Walker was found with a self-inflicted gunshot wound and Vaillancourt was shot in the back; both were taken to the hospital. Investigators said Walker and Vaillancourt had been living out of their car at the time.

Walker was charged with aggravated murder in Sgt. Johnson’s death, plus attempted murder and firearms offenses; Vaillancourt faced a charge of obstructing justice. If anyone knew Sgt. Johnson, his family, or had information about that early September morning in Draper, can you share what you know?