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SAN DIEGO — Another passenger stepped in when a man and woman got in a fight on a city bus in East Village Saturday night, and the confrontation left a man dead, police said.

The scuffle broke out around 8 p.m. near the corner of 14th and F streets, according to a San Diego Police Department news release. An argument between a man and a woman on the bus escalated until other passengers stepped in. By the time officers arrived, they found the man unconscious on the floor of the bus.

Medics arrived to rush the man to the hospital, but he was pronounced dead around 9:30 p.m., SDPD said. Police did not publicly identify the man, who was 28 years old.

Investigators said they are still trying to determine exactly what happened on the bus.

They learned that at some point during the initial fight, another passenger “physically intervened and restrained the victim for several minutes.” During that struggle, the other man passed out, going into “medical distress.”

How exactly the passenger was restraining the man, and what caused him to lose consciousness, remained under investigation Sunday. Police identified the passenger as Edward Hilbert, 55, and said he was booked into county jail on suspicion of murder.

Officials are still interviewing witnesses and hoping to learn more about the fight. A detective told OnScene TV that police are also looking into whether the woman was the victim of a crime beforehand.

Authorities urged anyone with information about the incident to call the SDPD Homicide Unit at 619-531-2293 or San Diego County Crime Stoppers at 888-580-8477.