I'm new to GMing, and one of my players (also new to RP), lets call him Dave, is having a hard time getting immersed in his character. Out of my 5 players, 2 are brand new, but the other new player is at least trying to do the RP part of it, although she still is figuring out the mechanics of it all. Dave on the other hand keeps saying that he's trying to learn it and understand it, but then puts no real effort into becoming more knowledgeable. Although they haven't outright said anything, I can tell the other players' fun is suffering as a result. We're 6 sessions in and I still have to stop and explain how to make a dice pool.
Dave's excuse is that this wasn't what he was expecting the game to be. He plays a Droid Bounty Hunter, and supposedly was under the impression that he was going to start out the game like a badass. When the first encounter with a NPC shopkeeper came along, he pulled his gun and tried to shoot him but failed all his rolls, so our Wookiee stepped in and finished the job. I guess this left a bad taste in his mouth, because he was incensed that a "mere shopkeeper" wasn't immediately vaporized by a bounty hunter. I think he also saw all the other players succeeding in their checks, and was frustrated that he didn't have a moment to shine. So over the next few sessions I tried to put him in situation's where Dave specifically could wreck shop, but he would run away from the action and hide because "If a shopkeeper is that tough, how will I survive against a street thug?"
I'm sure being an inexperienced GM also trying to learn the game didn't help, but does anyone have any advice or input on this situation?