A California man was charged with murder in connection with the death of California Highway Patrol Sergeant Steve Licon on Saturday afternoon.

According to NBC News, the suspected DUI driver—identified as 36-year-old Michael Joseph Callahan—pleaded not guilty during his arraignment on Wednesday.

Sergeant Licon was performing a traffic stop when Callahan's car—which was traveling along the right shoulder and not in the designated freeway lanes—struck Sergeant Licon.

Related: California Highway Patrol Officer Fatally Struck by Car