When reporting a hacker please put his name and steam id so its easy to find in our logs.
example:
In game name: nub
What server: zombie
Steam ID: STEAM:0:1:XXXXXXXX
Why they were banned: hacking
to get his steam id or name go to the console by hitting the ` key and type status the steam id will look like this STEAM_0:0:XXXXXXXX if you cant get to the console you probably didnt enable it you can do so by going to options/keyboard/advanced and check the box for console.