Anton Thibodaux was a mentally unstable man who was obsessed with astronaut Marga Janssen, later becoming a suspect in her murder as a result.
After being cleared, he was manipulated by the real killer, Colonel Dick Finley, who made him believe Vincent Beckwith was the murderer. As Beckwith was being led out of the SVU precinct, Thibodaux stole a pistol from a police officer and used it to kill him. Then, Finley tackled him and pretended to fatally shoot him in the stomach in self-defense. (SVU: "Lunacy")