I have a question or two…
Why take such an old rifle?
Did the rifle really need assembling and disassembling?
Did he really leave his screwdriver up there?
If he took up a disassembled rifle, assembled it, took the shot, then disassembled it to escape (he certainly didn’t look to be jumping off the roof and escaping with a long gun), why (or how) did he leave the gun fully assembled in a grassy ditch, wrapped in a towel, with a plan to return and pick it up???
In short, WTF was he thinking and why all the work to be surreptitious and then leave all the evidence lying around inside the murder search area???
Someone definitely took a shot and it tore his neck open, whether directly or as a ricochet from the top of his breastplate, instantly killing him in public. Whether it was this kid, with the gun they say, it APPEARS so, but there are questions that need answering.