Who is who **spoiler**

I would like to know who was who in the robbery. I figured a bit of it out but not all. Did the one trivia guy get killed at the bank by David and then the brother killed by Jack at the motel? I know the other 2 robbers were Jack and the dentist but in the scene I can't figure out who is who. There were 3 robbers in the bank and one drove the van into the bank. The driver was the dentist, the one who David killed was one of the brothers, so Jack and the other brother are the ones I really can't figure out. Which one went in to get the money and which one was at the window looking out?