HELP how do i find someones ip address on a steam game like counter strike!! VERY IMPORTANT!!!?

Question

ok about 2 months ago me and my firend found this person on counter strike that added us. we both were stupid and said that we were our actual ages( 13 and 14) and he said he was a 12 year old girl and we were like whatever. but she kept harassing us about being s*x buddies and stuff and how we were poor and to tell us her address. well today it got weird and he admited to be a guy acidently. so we went all fbi on the person and by interrogating 5 of his "friends" we found out he is a homosexual pretator. so how can i find his ip address using steam (yes i no you can because someone did it to me once and got it right) and please hurry so we can report him to the fbi

BTW: his name is (WASSUP) thunder bird and he'll try to act like someone your age of the opposite s*x if your a guy.

Answer 1

try the /whois nick_name command