A man was shot and killed during an altercation early Monday morning in Santa Ana that left four other men injured, police said.

Santa Ana officers responded to reports of gunshots around 12:45 a.m. at El Zocalo Mexican Grill & Seafood, 301 N. Tustin Ave.

Investigators suspect a physical fight broke out inside the restaurant when at least one handgun, later found by police, was fired and a man was fatally struck, police Cpl. Anthony Bertagna said.

“The shooting suspects attempted to flee, and security guards and patrons continued the altercation, and the other two suspects sustained nonlife-threatening injuries,” Bertagna said.

Two men were also shot. One is in critical condition and the other in moderate condition, Orange County Fire Authority Capt. Steve Concialdi said. The men were taken to Western Medical Center in Santa Ana, he said.

Another man was taken to St. Joseph Hospital in Orange and was in moderate condition with injuries including cuts and bruises and a rapid heartbeat, Concialdi said.

At least two of the men were initially considered suspects, although police said there may be one additional suspect.

Another handgun may also have been involved, Bertagna said.

More than 20 witnesses and patrons were waiting at the Santa Ana Police Department on Monday morning to be interviewed by investigators, who are hoping they may be able to shed more light on the incident.

Police shut down Tustin Avenue between First and Fourth streets during the investigation and reopened them sometime after 10 a.m. once the coroner removed the dead man from the restaurant.