I have never seen anything I suspect of being related to hacks. I haven't seen ANYTHING that would make me think he could get this score with 13 ppl on. I played on S1 using p90 a couple of times, and my best was around 70/17. If, as you say, he wasn't spawncamping, it is very hard for me to understand how he got this score. Knowing the weapon he used would help me understand.
That score is completely possible, though. The number of people that were in the game are the only thing that make me wonder. Whatever, like I said, I don't see him doing anything that looks hacky. I haven't even seen him get in first place for quite a while.
I wish people would simply have the maturity to not hack in the first place. We would never have to worry so much about whether people were hacking or not.