Real quick, regardless of whether or not the player is using an aimbot, attempting to call out players on the forums is against forum rules... so please don't do it. If you are suspicious of a player potentially cheating, you can report them via Ubisoft Support. This is not the place for hackusations.
Aimbot should be more like 100%. That player may have been using head shot buffs like body shots count as head shots.
The player could also just be good. I don't know the stats for a good sniper in this game, but on other FPS games, it's not uncommon to do really well if the player is any good. Sniping is a skill plus you need decent computer to keep lag consistent.