Requires a Dummy account
Open the command console: ESC > Gear Icon > Under the keyboard tab select Advanced > Check off Enable Developer Console
Press the ` button to open the console and type:
map ctf_2fort; hostname "boost"; sv_lan 0; sv_cheats 0; (I had to input this twice to be detected on my LAN for some reason)
That will create your match. Choose Sniper on the Red Team. Then type the following command:
Make the Dummy account a Demoman. Take him to an open area where you can snipe him and shoot him in the head.