While I'm sure this is very irritating, I'd recommend giving him the benefit of the doubt before sending him off to the stockades.

I'd go about it like you did before, but also point out that this is the second time in a week and ask if they can annotate your account stating that you're multiboxing so that this doesn't happen in the future.

Then, if it happens again, you're pretty sure it's personal and you can go for the throat.