Just a note on your second point.

[colorado_ufo]

Snipers aim for a center mass, as it is too easy to miss a small target such as a head or neck. They want to hit the target the first time, as they do not want to be discovered or be subject to counter fire. The bullet hit the neck, most likely, because the trajectory of a bullet rises, and he shot from an upper position downward. It was likely an error on the shooter's part that still accomplished what he set out to do.

Also, he looked to me to be young but too old to be a college student. He apparently did leave clues, including a handprint and footprint. This all looked planned.