A Washington man was allegedly poisoned with fentanyl and then fatally stabbed in the neck by a couple he met on a dating app, who then later tried to squat in his house following his reported slaying, authorities say.

Philip Brewer, 32, and Christina Joel Hardy, 47, allegedly killed 74-year-old Curtis Engeland of Mercer Island, Washington, according to prosecutors, KOMO-TV, KIRO-TV, and the Seattle Times reported.

It's unclear if the pair entered pleas or retained attorneys to comment on their behalf. 

Engeland was first reported missing by loved ones Feb. 24. His body was later found March 7 during a search over 100 miles away in Grays Harbor County, Washington, after cell phone evidence indicated the area was his last known location, according to Mercer Island police. 

An autopsy revealed he suffered from blunt force trauma to the face, a stab wound to the neck, and had an "unquantified amount of fentanyl" in his system, according to the Kings County Medical Examiner, KOMO reported. His cause of death was ruled a homicide.

The investigation revealed Engeland met Brewer through the Scruff dating app in January, KCPQ-TV reported, citing court documents.

During their first date at the victim's home, Engeland allegedly fell asleep while they watched a movie. When he awoke, Brewer was gone and so were his belongings - including his wallet, car keys, cell phone and social security card, authorities allege.

After Engeland's alleged murder, Brewer and Hardy attempted to move into his home, before making their way to Portland, Oregon, and later on, southern California, police said. 

On the way, they allegedly stole thousands of dollars from the victim and purchased a car.

"First and foremost, we must acknowledge Mr. Engeland's family - when this incident was first reported to police as a missing person, we hoped for a better outcome," Mercer Island Police Chief Ed Holmes said in a statement Friday.

"The family remained determined to help our investigation over the past few weeks and we hope some comfort can be found through the hard work being done to bring justice for Curtis and his loved ones. We appreciate the community's support as the police department was unable to share law enforcement-sensitive updates with the public until after our suspects were apprehended and know it was difficult to await answers in the wake of such terrible circumstances," Holmes said.

Brewer and Hardy are being held at a southern California jail, where they await extradition to Washington. A judge set their bail at $5 million.