Could it be that everything went according to plan except for the missed shot?
Probably.
Yes.
(somebody forgot to teach Crooks about windage which, if the kid was truly smart, he'd have had an app for that on his phone. Otherwise, it's evidence - ahem - of his 'handler(s)' being bureaucratically trained, rather than by someone with military background).
I still believe that the local LEO that climbed up to the roof interrupted the plan. It flustered the shooter so that he missed by an inch. Head shots are a smaller target and require concentration and steadiness.