|“||Well, well, well. Does your mom know you're here?||”|
— O'Brien just before being killed by his son
Born on February 6, 1967, in Providence, Rhode Island, William was a "connected man" and apparent sociopath who would commit arsons both for fun and profit, specializing in making them look like accidents caused by faulty wiring. In 1993, he set a fire that killed his wife Judy and made it look like an accident in order for him to claim her life insurance. He was somehow tracked down and arrested on May 5 of the same year. His then-ten-year old son, Connor (who William had often abused), caught him in the act and testified against him, sending him to jail. William then spent 17 years in prison for arson and first degree murder. In January 2010, his sentence was reduced to the possibility of parole in 2015. This drove Connor to become a serial killer, slashing the throats of random people in public places that reminded him of his father.
After a month and three murders, the BAU was called in and were able to catch him, but not before he had devolved into a spree killer. Ironically, once he had been arrested for his killings, Connor ended up in the same prison as his father. In the lunch line, Connor is handed a shiv by a fellow inmate and greets William, who, unaware that Connor was armed, mockingly replies, "Does your mother know you're here?" He is then stabbed to death by a furious Connor while the other inmates idly watch.
Since the episode focused mainly on Connor, it is unknown as to exactly how William set his fires, but Garcia mentions that he would make them look like the result of faulty wiring.
No profile of William was made by the BAU, since the episode was focused mainly on Connor, although he appears to be a sociopath.
William is partially similar to Rhonda Orr. Both were arsonists who killed their spouses in arson fires, which they made to look like accidents, in order to claim money from their life insurance policies.
- Unspecified dates:
- Connor O'Brien (his son; abused only)
- Five presumably victimless arsons
- Four victimless arsons set for profit
- 1993: Judy O'Brien (his wife; killed in a fire in order for him to claim her life insurance)