I don't know about wall hacks but the shaking/ insta head shots shows that this guy was using aim bot.
When he insta head shoted that Vagabond it made it very clear that something was up.
if you watch the kill at the bombsite you can see he was looking up at the boxes before he came around the corner. I didn't notice it until he went through the tunnels for the last kill and he was just straight looking at the dude while walking down that hall.l