Police say the 27-year-old man, whose name was not immediately released, died Wednesday at a hospital.
Witnesses told police the man was fighting with someone during the Angels-Athletics game on Monday when a third person came from behind and punched the victim in the head. The man then fell and hit his head on a concrete step near a stairwell.
Police are unsure what led to the fight and who started it. Investigators are reviewing surveillance video. No arrests have been made.
"We will continue to cooperate with the Anaheim Police Depart in the investigation," team spokesman Tim Mead said. "We've been working with them since Monday evening. It's an unfortunate incident. Hopefully, anyone with knowledge or awareness of what happened will come forward and assist in the investigation."
Mead pointed out that the incident happened at 8:45, the game having ended at 8:38.
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