TULSA, Oklahoma - Murder charges have been filed in the death of a man Tulsa Police say was beaten at a convenience store.

William Cooper is accused of assaulting Brobegger Willis in January 2016. Williams died in July 2017 and the Oklahoma Medical Examiner's Office declared that Willis' death was caused by complications of blunt force trauma.

Police said an autopsy listed the manner of death as homicide.

Cooper "hit the victim multiple times causing severe head injuries," according to Sgt. Dave Walker at the time. Police said Willis was talking to a woman Cooper used to date when Willis was attacked.

Willis had massive head injuries and underwent surgery at a Tulsa hospital.

Police arrested and charged Cooper with assault, but the charges were dismissed because witnesses failed to appear.

Police said Willis' death will be Tulsa's 74th homicide for 2017 "due to the fact that the homicide death occurred on July 5th, 2017, and we began the murder investigation at that point."