It wasn’t unusual for Cassandra Bjorge to run away from her grandparents’ Gwinnett County home. During a 16-month period, police were called to the home 18 times.

On April 1, 17-year-old “Cassie” was gone again, and her grandmother asked for help in a Facebook post.

“Please spread the word … PLEASE BE ON THE LOOKOUT FOR CASSIE,” Wendy Bjorge posted.

MORE: Tire iron used in Gwinnett slaying

It is possible that Bjorge and her husband were killed the same day as her post, according to police. And their granddaughter and her boyfriend are accused of killing the couple, police said Thursday.

On Saturday, Wendy and Randall Bjorge, both 63, were found dead inside their Lawrenceville-area home. Their throats had been slashed, and they had been punched, kicked and beaten with a tire iron, police said. Investigators believe the couple may have been dead for as long as a week before being found. Police have not determined what may have led to the killings.

“This is a very unique and disturbing case on so many levels, and detectives are still exploring motive,” Cpl. Deon Washington said Thursday. “We may never find a scenario that makes sense to a reasonable person.”

The alleged violent acts by Cassie and her boyfriend, 19-year-old Johnny Rider, continued for several days, according to police.

Officers were asked twice in two days to check on the Bjorges but noticed nothing suspicious at the home.

Rider and an unidentified female allegedly attacked his sister and her boyfriend late last week at another home near Lawrenceville. It was at that home where investigators found a vehicle belonging to the Bjorges, and officers returned to the Bjorges’ home on Furlong Run. The bodies were found by officers who forced their way inside the home.

Rider and Cassie then allegedly stole a vehicle belonging to Rider’s sister. That vehicle was found parked at a Suwanee apartment complex early Sunday, but Rider and Cassie refused to surrender, and a SWAT team was brought to the scene.

When SWAT officers entered the apartment, Rider and Cassie were found with self-inflicted wounds to their wrists. Both were taken to Gwinnett Medical Center for treatment, and both were charged with two counts each of murder and aggravated assault when they were released.

Additional charges for Rider include aggravated battery, theft by taking, credit card theft, entering an auto, obstruction and possession of tools during the commission of a crime, Gwinnett jail records show. Cassie’s arrest violated her probation for a prior crime as a juvenile, but juvenile records are not open to the public.

During his first court appearance Thursday, Rider’s arm remained wrapped in bandages due to his injuries. Cassie is expected to be in court Friday. Both are being held without bond.

Additionally, investigators are looking for other teens who may have been inside the Bjorges’ home.

“These teens were unrelated to the actual homicides, but they may have information that proves to be critical for the homicide investigation,” police said in an emailed statement.

Parents with teenagers who live in the Furlong Run area, located off Steeple Run, were asked to contact police with any information regarding who may have been in the Bjorges’ home between April 1 and April 8.

Wendy and Randall Bjorge are survived by their daughter, Amanda; son, Christopher; and four grandchildren, according to their online obituaries. Randall is survived by two brothers and a sister, and Wendy is survived by a brother. Tim Stewart Funeral Home is handling arrangements, but plans for a memorial service have not been announced.

Cassie’s mother, Amanda Sterling, told Channel 2 Action News she “needs everybody’s love and support and strength” as she processes the charges against her daughter in her parents’ deaths.