What are your options in this scenario?

I saw this video and it got me worked up. I would like to know what you should do in this situation if you were one of the bikers watching his buddy get beat up while there's another man brandishing a shotgun. The bikers may have started the altercation and you can see the shotgun guy later checking on the biker that was assaulted as he lay on the ground. For this scenario I only want to address the section of the video from the point where the biker was assaulted and beaten while he is no longer able to defend himself.What can you do legally to defend yourself and the biker being assaulted? I would be afraid for my life and for the life of the biker being assaulted. I would be afraid that if I tried to draw my weapon to intervene that the guy with the shotgun would shoot me. The guy with the shotgun appears to be preventing anyone from intervening. If I could have without getting killed myself, I may have shot the guy with the shotgun and kept fat boy with his knife at bay while letting others pull the attacker off the biker. This could have been so much worse and I'm glad that no one got shot.I think I would have done whatever I could to keep myself and the other biker alive or from being seriously injured. If that means going to jail, that's better than dead right?If I am misguided please forgive my ignorance.YouTube video via /r/CCW https://ift.tt/2Z08dtw