My brother was shot by another bar patron unknown to him. is the bar liable?

he was out with several friends when a guy came in and was harassing the female patrons. finally a girl told the guy to leave them alone and threw a drink at him. he retaliated by throwing a beer bottle back at her. he then walked outside and came back in with a gun and shot into the crowd. the bullet struck my brother and shattered his femur in 5 pieces. is the bar at all liable?