WELCH, Okla. — UPDATE: Ronnie Busick is being evaluated by a medical expert to determine his competency. His trial will be put on hold until February 22.

A suspect appeared in court Monday after investigators made a break in the 1999 disappearance of two Welch girls. 

FOX23 learned officials charged Ronnie Busick in connection to the girls' disappearance. Busick appeared in court for the first time April 30th.

Backstory:

Ashley Freeman and Lauria Bible were 16 years old in 1999, when they planned a sleepover to celebrate Freeman's birthday.

The day after the sleepover, firefighters found Freeman's parents, Danny and Kathy Freeman, shot to death in their burned-out home. The girls, however, had disappeared.

For years, investigators searched for answers, interviewed several potential suspects and pleaded for information surrounding the girls' disappearance.

FOX23 has been following the case for years, reporting in 2017 that "extremely valuable" information was turned over by Craig County Sheriff Heath Winfrey.

Suspects Named:

Officials said they charged Busick Sunday in connection to the case. He faces four charges of first degree murder, two counts of kidnapping and a final count of arson.

Busick was in custody in Newston, Kansas, according to investigators.

He arrived at the Craig County Jail around 5 p.m. Wednesday.

WATCH: FOX23 was at the scene when Busick arrived

At least two other people were involved in the case, they said. Those suspects, identified as Warren Phillip Welch and David Pennington, have since died.

Family of the victims learned the girls were likely kept alive some time after their disappearance, but they have likely since died. Their bodies have not been recovered.

Details From The Newly-Released Affidavit:

A newly-released affidavit claimed Welch kept photographs in a leather brief case that showed the girls bound and gagged at his Picher home during their last days. According to the affidavit, multiple people said they had seen the pictures, but the suspects reportedly threatened them.

The affidavit claimed the girls were tied up, drugged and raped before they were killed. It said the girls were strangled and dumped into a pit, which may have been a mine shaft near Picher or a cellar that was later covered in concrete.

SEE MORE: FOX23 has a look at the area where the girls where reportedly held

Multiple people told investigators that both Welch and Pennington been dealt methamphetamine, according to the affidavit. One person reportedly told investigators that Pennington had said that Freeman and Bible had entered a room where the Freeman parents were buying drugs on the night of the crime.

Another witness reportedly said that a conversation between Welch, Pennington and Busick had implied that the Freeman parents had been murdered over a debt. That witness said that the suspects had also hinted that they had taken the two girls and eventually killed them, according to the affidavit.

The document said an insurance card found near the scene connected to a car that investigators believed to be connected to a vehicle in Welch's possession helped them in the case.

It said that the suspects had threatened the lives of people who may have had information about the crimes.

Court Appearance:

Busick appeared in court with public defender Gretchen Mosley April 30.

Mosley specializes in cases involving the death penalty. Though officials have not mentioned the possibility of seeking the death penalty, Mosley said she wanted to be involved with the case, because she believes prosecutors may seek it.

Busick's next court date is May 11.

Remaining Questions:

Investigators said they still need people to come forward about where the girls' bodies may be. Anyone with information is urged to contact the Oklahoma State Bureau of Investigation at 1-800-522-8017 or via email at tips@osbi.ok.gov.

Officials said a private reward for $50,000 still stands for information related to the location of the girls.

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