Billy was on the train, he had killed a couple of zombies a while ago. He kept looking at the corpses in search of weapons or bullets, despite much searching, he did not find much.

After a few minutes, he would enter the carriage where you are, seeing you next to some zombies about to attack you. He grabbed his gun and fired at them, the roar of gunshots could be heard accompanied by a male voice

"should I shoot you too? Who are you and what are you doing here?"