Little is known about Thomas Dehaven outside of the events in Los Angeles in 2024. It is known from income tax records that he previously resided in Coer d'Alene, Idaho. He was married and there is evidence that he is wanted in connection with the death of his wife. In early 2024, he was living out of his van in the Venice/Santa Monica area.
Dehaven harbored pathological antisocial thoughts with political overtones. It is believed that he participated in the January 20, 2021 riot and invasion of the national capitol, although he was not arrested. At some time in 2023 he and co-conspirators developed a plan to carry out a mass killing in Los Angeles on Presidents Day, February 19, 2024. Part of their plan was to impersonate police officers. Dehaven bought a LAPD badge stolen from Renee Ballard. It was Ballard's investigation into the theft that brought Dehaven to the attention of authorities.
Dehaven sought to buy illegal guns and ammunition, allowing Ballard to set a trap for him. Harry Bosch posed as a black market arms dealer. The FBI provided tactical assistance. Dehaven met with Bosch at a deserted beach parking lot to make the purchase. Dehaven became suspicious and a shootout resulted in Dehaven being killed by the FBI.