If he made a gag request for the players that wrote in chat that time, then it should match just fine! :-D
Also I think he ban request was intended for roofcamping but not teamkilling?! A demo is usually required so we can see if something was done intentionally or just a possible mistake... But roofcamping is forbidden in general and the ct can't get up there by accident. Furthermore he already got banned before for roofcamping. I also validated the timestamp. So my guess is that a screenshot should be proof enough...