James Whitehead was shot by Orange police captain Robert Arnold in July of last year during an altercation over whether he could return an item he had purchased.
According to the suit, Arnold was in the store, followed Whitehead when he left, got in Whitehead's car and shot him in the chest and "unbelievably did what has been called a 'victory dance,' showing no remorse for this senseless killing."
Arnold was no-billed by a grand jury investigating the incident.
Meth and THC were found in Whitehead's system in an autopsy, according to a newspaper report.
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Whitehead, 28, had served two tours of duty in Iraq, the suit says.