Instead of shooting himself through the jaw he shot off his jaw and was unsuccessful in killing himself, but he was still put to the guillotine.
To pull a Robespierre is the act of successfully trying to kill oneself esp. attempted shootings through the skull (by holding a gun under ones jaw), but turning out unsuccessful and shooting off ones jaw
Get a gun
put it to your jaw like a gangsta (making sure the gun will only shoot off your jaw)
* Now you have successfully pulled a Robespierre
Situation: Jim is in the hospital for attempted suicide
Bill to Mike: "Dude, what happened"
Mike to Bill: "Nothing, but Jim pulled a Robespierre. I heard he did it for the lulz"