TULSA, Oklahoma - Police say a man is "extremely critical" after receiving massive head injuries during an assault Tuesday evening outside a midtown Tulsa store.

Officers say just before 6 p.m. police responded to a convenience store in the 400 block of East 11th Street in response to a fight.  Police said when they arrived they found a man in his 30s that had been beaten with metal tool.  

EMSA took the victim to the hospital, where he underwent surgery.

Police say they are looking for 26-year-old William Brent Cooper.  

Wednesday morning, police got a tip called in to the News On 6 that Cooper was at the Day Center for the Homeless in downtown Tulsa, but officers were unable to find him.

According to witnesses, police said the victim was outside the convenience store Tuesday evening talking with two women when Cooper arrived and began hitting him with the tool.

Cooper is described as a white male, 5-feet-10-inches tall and around 155 pounds.  Tulsa Police ask anyone with information to call Crime Stoppers at 918-596-COPS.