You would shoot back at the muzzle flashes ...
He would have been hit or dead much sooner than what it took him to kill 50.
3 rounds from 4 shooters would have definitely landed at least 3 kill shots on the target but with a maximum of about 12 casualties from rounds that passed through or by the target.
Those casualties would not all have been fatal either...
Gun grabbers are so full of XXXX that they smell like a rotting pig sty.
of course I am assuming that the 4 shooters would at least be sober, and moderately exercised “bouncer” types...
I have gotten to the place where I think most people should do that kind of math in their heads, before they go to any type of group social event where firearms might be restricted. Calculate a few scenarios, before you leave... or just don’t go.