The suspect, Brady Oestrike, 31, is also dead. Police said he killed himself after crashing his car during a police chase.
The body of Brooke Slocum, 18, was found in the trunk of Oestrike's car Thursday. Investigators believe he kept her confined in his home for at least day after her boyfriend, Charles Oppenneer, 25, was killed, Wyoming Police Chief James Carmody said.
Carmody said police have not determined how Oppenneer was killed. His body was found Wednesday near his vehicle, but the head was missing.
Items seized from Oestrike's home include guns, knives, ammunition, items belonging to both Slocum and Oppenneer and restraints allegedly used to confine Slocum, Carmody said.
Carmody said emails between Oestrike and Slocum suggested they arranged a sexual encounter after getting in touch on Craigslist. The meeting was to be in a park near where Oppenneer's body was found. He was to be present.