I know I am being an armchair quarteback here, and I am not in the bikers shoes at that moment, but I think as soon as he turned away and had tucked that pistol in his waste band that he would have caught a pretty massive rabbit punch followed by a serious beat down. His buddy may have had a gun too but he would catch a round or three after Mr. thief gave his pistol away, provided it was actually loaded.
It is a quick thing to see how a bike jacking can occur. I got lucky as a young sailor when I toon down a bike thief at a resturant by punching him in the back of the head as he tried to ride away. He went hard but didn't have a pistol on him. I'm out of shape now and nowhere as good as Mitch in the ring, but I also don't stand by and let **** go down if I can stop it.
Glad the Policeman was there...