Fresno County sheriff's Sgt. Kevin Lolkus says 39-year-old Amado Vargas was arrested on suspicion of assault with a deadly weapon.
Lolkus said Vargas first threatened people with a knife, which was wrestled away from him.
Police said Vargas then ran into a room with a gun safe, took out a handgun and fired multiple shots.
The 49ers lost to the Seahawks 23-17.