Answer:
As the soldiers were coming to arrest the members of the Committee Robespierre, knowing that death by guillotine would await him if he was executed, put a pistol to his own jaw and shot himself. He failed to kill himself and only succeeded in shooting off his jaw.
He tried to kill himself because he knew when he was arrested he would get his head chopped off by a guillotine and he didn't want to die like that so he shot himself in the jaw hoping it would reach his brain and kill him but he just ended up shooting off his jaw.
