Simi Valley police officers were responding to a loud music complaint at approximately 10 p.m. Sunday at The Chop Shop Bar & Grill in the 4000 block of Valley Fair Street when they found an unconscious man lying on the ground.
Investigators discovered the victim was suffering from a serious head injury from being punched in the face and falling to the ground, where he struck his head on the pavement.
The victim was taken to Los Robles Hospital for treatment.
Authorities later arrested Gregory Monsour, 36, of Simi Valley for the attack. Investigators found out that Monsour and the victim knew each other, but what led up to the attack remains unknown.
The victim's identity and condition were not immediately released.