Jermaine Ulinwa told KGW-TV, Portland, Ore., the beatings happened in Portland's Old Town district Saturday.
Ulinwa said he took Lillard's picture with his cell phone after spotting the Portland Trail Blazers star walking toward a parking lot with several other people.
"Damian Lillard was upset that I took his picture," Ulinwa said, adding he offered to apologize but within minutes the discussion turned into an all-out fight.
The fight did not involve Lillard, the Salt Lake City Deseret News reported, but it did involve members of Lillard's entourage and Ulinwa's brother Phil.
A Portland police spokesman said Lillard is not a suspect in the incident.
A spokesman for the Trail Blazers said based on preliminary reports, no players are considered suspects in the case.
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