Video captured Riverside County sheriff's deputies repeatedly hitting a man with a baton. Authorities say he later died at the hospital.
The man has been identified as 33-year-old Ernie Serrano of Jurupa Valley.
Deputies say Serrano refused to comply with their commands.
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They say he tried to grab a security guard's gun, but his family disputes that.
"This doesn't happen to people in Sherman Oaks or in the Valley to white people in the store. You don't see a cop run up to them and hit them with a baton," Humberto Guizar of the Justice X Legal group said.
"He was not hitting nobody back, he was not fighting like they said he was," said an emotional Maria Serrano, the mother of Ernie Serrano. "He was taking the hits and they put him on the floor, and they killed him. He died right there. He didn't die at the hospital. He died right there."
Lawyers of the family say they plan to file a claim that would allow them to see surveillance video from inside the store.
An autopsy for Serrano is set for Monday.