If he cheats, he is generally very coy about using them, to the extent that he will purposely ignore people to over compensate. It will likely be difficult to nail anything down conclusively, especially when people keep saying he hacks while he is in server.
Best thing to do, is try to just camp as vaga, to the extent that he has no reason to know where you are, and just kill him alot. Hackers tend to hack harder after they get killed a bunch by someone talking shit.
I hit Brett right in the feels.