A man broke up a fight on a San Diego bus, only to be charged with first-degree murder.

Edward Hilbert, 55, was arrested after police responded to a call from Metropolitan Transit Service officials about an incident on a bus Saturday night, CBS8 reported.

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Lt. Steve Shebloski of the San Diego Police Department said that Hilbert had intervened in a fight between a man and a woman on the bus and held the man back for several minutes. Shebloski said that the man lost consciousness while Hilbert restrained him, and by the time police arrived at the scene the man was "unresponsive" on the floor.

"Officers called for medics and performed life-saving measures until paramedics arrived," Shebloski told the outlet. The man was then pronounced dead at a local hospital.

Fox News reached out to the San Diego Police Department for further information but did not immediately receive a response.

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Cops arrested Hilbert on a first-degree murder charge, according to records, and he is in custody at San Diego Central Jail, where he is being held without bail. He is scheduled to be in court for arraignment Wednesday afternoon.