At least the NFL can have somewhat of an excuse when it comes to violence at Candlestick. It's not just Raiders and Niners fans who can get into a tizzy in Bay Area games; Cal and Fresno State fans can sure get in on the action themselves.
According to Bay City News, a man was left beaten bloodied and unconscious after a verbal altercation between rival groups of Golden Bears and Bulldogs fans just after kickoff. He suffered a broken nose and lacerations to the back of the head. The suspect is being held in custody. It's hard to tell if Cal or Fresno fans had tickets to the game since the parking lots are supposed to be cleared prior to kickoff, so it's not known if these are fans of the game or just various locals looking to stir up trouble.
It's hard to say whether you can call this violence has any bearing on the previous Candlestick violence. But it certainly is another black mark on the Candlestick Park environment and a proper response by security at the game.