Police in Wyoming told reporters that the victims had arranged to meet Brady Oestrike, 31, through one of Craigslist's online sex personals sections.

According to emails found by investigators, pregnant Brooke Slocum, 18, had arranged to meet Oestrike for a sexual encounter - but only if he paid for it.

She planned for her boyfriend Charles Oppenneer, 25, to be present at the time.

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However, when the young couple arrived at Oestrike's home, they soon found themselves in a "hellish environment", filled with dozens of firearms, knives, ammunition, computers, cameras and electronic monitoring devices.

According to WOOD TV, Brooke was held prisoner by Oestrike for five days before she was strangled to death. Her body was found in the trunk of Oestrike's car on Thursday.

She was eight months pregnant at the time of her death.**

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Chief James Carmody says Brooke's boyfriend was found decapitated in a park a day before they uncovered her body. Investigators believe it was some sort of trauma to the head, but the nature of that trauma is unknown.

“We don’t know what trauma was caused because after he was murdered, his head was removed by the suspect.

“We have not been able to locate his head after a very thorough and exhaustive search.”

Oestrik, who fatally shot himself in the head after crashing his car during a police pursuit, has an extensive criminal history, including two domestic assault complaints filed by his ex-girlfriend.**

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Investigators have since made contact with the ex-girlfriend and she is, thankfully, alive and well.

Police are now being assisted by the FBI, and are currently investigating if there were other possible victims of Oestrike.** **