A skull found in Michigan last week was that of a man decapitated in 2014 while he and his pregnant girlfriend, who was also killed, were with a man whom they met via Craigslist, authorities said.

Authorities used dental records to identify Charles Oppenneer, who was 25 when he was killed in the Grand Rapids suburb of Wyoming by Brady Oestrike in July 2014. Brooke Slocum, 18, also was killed by Oestrike, FOX 17 of Grand Rapids reported.

MEXICAN BUSINESSWOMAN DECAPITATED AFTER 'FAMILY' WOULDN'T PAY' RANSOM, REPORTS SAY

"It was just a long, unanswered question and more than anything, we're just happy to report to the family this piece of information so that we can have some closure for them," Wyoming Police Capt. James Maguffee said.

Oppenneer and Slocum -- who was eight months pregnant -- met up with Oestrike at a park in a sex-for-cash deal, authorities said. During the meetup, Oestrike beheaded Oppenneer and kidnapped Slocum and held her captive for several days.

Oestrike, 31, killed himself while fleeing from police. Slocum was found dead from strangulation in the trunk of a vehicle, the station reported.

Oppenneer's skull was located March 26 on private property in northern Kent County, MLive.com reported.

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"This case was especially dark and, frankly, disturbing and saddened all of us that this sort of thing can happen, outside of a fictional setting, for sure. and impacted our police officers very deeply," Maguffee said. "There was a lot of hurt and soul and effort and pain involved in this investigation, and it just really touched us. It did then and it continues to today.”