That's one of the reasons in cases like these you still need to PROVE the event ~ and the cops appear to have neglected to do anything more than the most cursory examination of the situation.
So, where's the blood? If the guy was on top of him when he shot him, then where's the blood?
Call me crazy, but I prefer to focus on facts that have actually been disclosed. Just because police have not stated he was soaked in the 'victim's' blood, doesn't mean there is not blood transference to the shooter.