The store clerk refused to sell you beer because you're under twenty-one.
You shot him with your pistol and took the beer and now you're on the run.
You got in trouble with the law before and now you're in trouble again.
Killing a man over beer is disgusting, you'd better go turn yourself in.
The cops will eventually catch you and your fate will be sealed.
If you don't turn yourself in to the police right now, then I will.