Sorry, we can't process reports of game violations without proof (video).
That guy was flying all over
They probably won't accept it for the following reasons:
Noted, haven't got a clue how to make video. Suggest you follow player, since he was taking off like a helicopter, landing and firing from places noone playing normally can come.
Here are some free recorders you can try:
Personally i use Shadow Play in Geforce Experiece, though I think it requires a GTX 650 or better to actually use it.
Customer support service by UserEcho