Covina police say the assault happened on Aug. 17 at Clancy's Sports Bar at 961 N. Azusa after two men were involved in a game of pool.
After the game, the victim went to the restroom.
Moments later one suspect was seen walking into the restroom holding a beer mug. He was seen on video a short time later leaving the restroom and putting the mug on the ground. He later exited with a female companion.
The victim was hit in the head and knocked unconscious in the restroom, police said.
Police put out a call for help from the public and say they received multiple tips. That led them to arrest the alleged assailant as well as two others who were with him in the bar at the time. The role of the others in the assault was not immediately clear.
Police arrested Vidal Larios, 40, of Glendale, Angel Franco, 23, of Baldwin Park, and Elizabeth Franco, 40, of Baldwin Park. They were booked at the Covina Jail.
Larios was also held on a parole violation
The possible motive behind the attack has not been disclosed.