Do u think its right to hit a girl?

okk,so this guy on my bus (freshman, 16 years old, 300 pounds) was making fun of this chick for being ! then off the 1st bus stop, the girl's gf (16, around 170 pounds, junior) pushed him because he called them *******, then he punched that girl and knocked her out for 2 minutes! i saw the whole thing! then three cops and an ambulance came, the cops asked us and we had to tell the truth, the SAD part is he has lots of ** friends on the bus that was defending him! and after i reported him, he was arrested, then his friends say they will beat me up! D; im scared wat do i do??