Originally Posted by will76

I think they had a guard, someone unlocked it to let him.

Crowe shoots his gang because he was mad they killed Bale, and there was no way he could get on the train and look weak to his gang. He wanted to forfill what Bale started so Bale's family would get the money. Basically he grew a conscious and did a good deed. Like he said earlier in the movie doing good deeds is contagious and he couldn't do anything good and run a gang like that. He also knew he was going to hop off the train around the bend, so he wasn't going to end up in jail but he could no longer be the bad guy he was and what was needed to run his gang.

hope that helps. next time no more bathroom breaks for you, you missed some key parts