A former mixed martial arts fighter was sought by Denver police Friday after surveillance footage showed him knocking out another man inside a bar earlier this week.

Melvin Guillard, who fought in the Ultimate Fighting Championship (UFC) from 2005 to 2014, was seen on video obtained by TMZ Sports taking the man out with one swift punch at Bar Standard in Denver.

The website reported that the incident happened around 2 a.m. Monday morning and a police spokesman said witnesses identified the 35-year-old brawler as the attacker.

After the man hit the floor, a woman tried to go after Guillard but the two were kept apart by patrons. Another patron was seen tending to the unconscious, unidentified victim. It was not clear what caused the scuffle.

TMZ reported that a warrant is now out for Guillard’s arrest.

The fighter amassed a 12-win, 9-loss record during his UFC career, with one fight ending in a no contest. Eight of the 12 wins were by knockout.