Nothing having to do with the police would be coming to my mind.
I would consider myself dead already. I would try to see if I could deflect the gun to let others in and take they guy out.
I would also like to see legislation what would exonerate anyone killing the perp on the spot.
Any animal pulling a stunt like this should know up front they won’t leave the train car breathing.
Apparently, the goat humper’s gun jammed. Had everybody behaved like sheep he would have had time to clear it and shoot everyone in the carriage.