A teenage girl, along with her boyfriend, kicked, punched and beat her grandparents with a tire iron, according to warrants.

They’re accused of finishing the job by stabbing the elderly couple in the throats.

Cassandra Bjorge, 17, and Johnny Rider, 19, were charged Wednesday with the murder of Wendy Bjorge and Randall Bjorge.

Cassandra Bjorge was booked into the Gwinnett County Jail at 8:25 p.m. Wednesday. Rider was already there. He was booked Monday on three counts of aggravated battery, one count of battery and one count of theft by taking. Two murder charges were added Wednesday.

Gwinnett County police officers found Wendy Bjorge and Randall Bjorge dead in their home off Furlong Run in the early hours of Sunday morning. But police said the couple had been dead for about a week before that.

During that time, officers believe other teenagers not related to the murders may have been in and out of the house where the dead couple lay. Officers are asking local parents to talk to their teens about whether they were in the Bjorge house during that time.

“These teens were unrelated to the actual homicides, but they may have information that proves to be critical for the homicide investigation,” said Cpl. Deon Washington.

Other members of the Bjorges’ family noticed the 63-year-old couple’s absence early last week. They began asking Gwinnett police to check their house.

“Gwinnett County Police responded to the location several times beginning April 6 and attempted welfare check by the request of family members,” Washington said. “At the time, there was no obvious cause to enter the location by force.”

It was a violent domestic incident at Rider’s family house off Rambling Woods Drive in Lawrenceville Saturday night that led police to figure out what happened to the Bjorges.

Rider and Bjorge reportedly sprayed his sister and her boyfriend in the eyes with pepper spray before hitting them both over the head with a baseball bat, according to a police report.

When officers got to the house, they could see blood on a wall and door frame. The smell from pepper spray lingered in the air.

Officers didn’t find Rider or Bjorge at the house, but the did find a car they soon discovered belonged to the elderly Bjorge couple — the couple nobody had heard from in several days.

“Because of the crime at hand, officers decided to again make a welfare check at their home,” said Detective D.C. Smith.

This time, when nobody answered the door, officers went inside.

“Wendy and Randall were found deceased in the upstairs area of their home,” Smith said. “Their deaths were apparent homicides.”

He said detectives and crime scene personnel worked through that night to find Bjorge and Rider. Eventually, officers found them hiding out in the 800 building at the Residences at McGinnis Ferry at 4000 McGinnis Ferry Road in Suwanee.

They refused to come out for police.

So officials sent the SWAT team into the apartment, where they found that both Bjorge and Rider had tried to kill themselves by cutting their wrists. Both teens were taken to Gwinnett Medical Center for treatment before they were transferred to Gwinnett County jail.

They’re being held without bail, according to the jail log.

Both teens will be in court for their preliminary hearings April 21 at 1:30 p.m. The hearings may provide more answers, but Washington said he doesn’t expect the crimes to make sense.

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