The Alameda County Coroner confirms Desoni Gardner, 20, died of a gunshot wound.
Social media posts indicate he is Vallejo rapper "Lil Theze."
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Surveillance video from a Chevron gas station shows Gardner was with a group who attempted to rob Joyner while he was pumping gas.
Joyner fired at the group, and was shot six times in return.
He is still in the hospital recovering from his injuries.