There are quite a few questions at work here! Let's think about it.

There isn't an example of outright criminality in this story. Is Dave a criminal for killing Jenny? He has certainly misbehaved by bringing the gun to work with him, but he doesn't mean to shoot Jenny. He does lie to the others about what he has done. He also then shirks his responsibilities in terms of paying Jim back for the mule, whose death he has caused, so we can argue that he commits a criminal act at the end of the story by fleeing. He has created this mess, but he hasn't stayed to fix it or pay compensation for it.

This leads us on to the other questions, however—why is Dave so irresponsible? He is seventeen when this story takes place, and he spends most of his time complaining that others don't trust him to be a man. They expect him to work like a man, but his mother tells him he is only a boy, and therefore he is desperate to have a gun because he feels this will make him an adult. Ultimately, of course, he proves those around him right by being unable to handle the gun responsibly, but is this entirely his fault? Having the gun makes him feel strong, like he could kill anyone, "black or white." He also clearly feels that his family needs a gun—why?

The racist society in which he lives clearly makes Dave feel insecure. It holds him back from growing up because he is perceived as a "boy" not only by white people, but by his own family; at the same time he evidently does not feel that he is safe as a black person. So society and the behavior of his parents might be said to have influenced how he acts.

How do you picture Dave in a few years, then? This is a good question. He is an immature person who makes rash decisions, but might he have been changed by the situation with Jenny? How might he be different if he escapes the clutches of his family and his town?