Let me be honest in my own opinion, this was invalid proof/not clean evidence for me. Here's the reason:-
1) Shotgun hitbox is very huge, so that player can hit someone else without even need to aim at their head/body.
2) You are running into him which is making this evidence poor, you run into him, he can hit you easily with that.
3) A single proof can't prove anything (Unless he's very obvious)
4) Fighting in an open area would be much more desirable. (interior is a little bit tricky)
For me, this is invalid but I'll wait for other admins response.
TIPS: If you're trying to catch aimbotter, try circling him around in a very close range.