This can easily done by creating a LAN server with a 2nd computer with a limited steam 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;
That will create your match and your 2nd PC should detect the game under Community Servers on the LAN tab. If it does not, run the command again. I find I need to run it twice to detect for some reason.
Put yourself on one team and the opponent on the other. Pick spies for both players and have the dummy account take the revolver out and simply stab him in the back.