The incident happened during a benefit dinner.
The Sacramento Bee reports a man smashed a pie in mayor Kevin Johnson's face. His spokeswoman says the mayor then hit the protester.
The East Bay Express reports Johnson tackled the man and it ended in a bloody brawl.
Appreciate everyone. I'm doing fine. Thank you to Sac PD for being there. Be safe everyone.— Kevin Johnson (@KJ_MayorJohnson) September 22, 2016
The mayor's office say the man, Sean Thompson, was taken to the hospital for a minor injury and faces a charge of assault.