A sister told the detective that one of Thornton’s former boyfriends had previously told her that the couple took a trip to Green River in 1977 to pan for gold, but the pair parted ways after a fight. The family had last seen Thornton when she visited her uncle in Biloxi, Mississippi, in June 1977, the documents state. She was “notably pregnant” at the time.

Alcala was traveling the country during the summer of 1977 after his parole officer granted him permission to drive from California to the East Coast to visit family, court documents show. He left California on July 2 and returned on Aug. 6. He later traveled from California to Mexico from Aug. 11 to Aug. 20 that same summer.

Court documents do not state why Alcala was on parole at the time.

Investigators reviewed the other photos found in Alcala’s possession and determined that the same motorcycle Thornton is pictured riding — a blue and white Kawasaki — was also present in the photos of Alcala’s other victims. During previous investigations, the motorcycle had been found disassembled in Alcala’s Seattle storage unit, according to the documents.

Alcala is on death row at the Cocoran State Penitentiary in California for previous murder convictions. If convicted of the Wyoming charge, he could face additional charges of life imprisonment or death.