Shouldn't the punishment for attempted murder be as severe as the punishment for murder no matter your ethical scheme? If your ethical scheme is based on universal moral principles (deontological?), then surely whatever is inherently bad about firing a gun at someone with the intent of ending their life is present whether or not you have good aim. And if you are a utilitarian, then it would seem equally risky to the populace to release a person who has expressed a tendency to try and kill people back on the streets.