"One need not succeed in a crime to be punished for the crime. Take enough sufficient steps towards the commission of it, and you're in deep enough. Otherwise, thwarted efforts would go unpunished."
What is the crime? He was sleeping in his car, about to commit a crime, maybe? I think a first year law student should be able to get this guy off.
Unless, he was in the getaway car and we have only half of the story.
He was illegally in possession of a stolen car and a bunch of hypodermic syringes, add in the cap pistol, the disguise and the demand note all being discovered at or about the scheduled opening time of the store and the fact that most cash registers are electronically-controlled and likely empty at opening time and I think they could prosecute him on capital-stupidity charges.