Too short!
Heh!
On a random note, if you see any cool mods for TF2, let me know. I'm not against putting them on our server if they are cool enough!
Read the comments and the information listed by the author on the youtube link. You have to download the file and rename it to sentry_client and sentry_client_found and put them in a weapons folder in sounds folder of TF2. I'm not sure if those are the exact instructions so it'd be best to check the comments on youtube to make sure