The mother of the teen accused of playing a role in the murder of her grandparents is speaking for the first time.

On Wednesday 17-year-old Cassandra Bjorge was formally charged in the murders of Wendy and Randall Bjorge, both 63 years old. According to police Cassandra and her 19-year-old boyfriend Johnny Rider beat the Gwinnett County couple inside their home nearly a week before their bodies were found on April 8. Police said the cause of death for both victims was an incision to the throat and blunt force trauma.

TIMELINE | Teens accused of killing Gwinnett grandparents

In a Thursday news conference with her attorney, Cassandra’s mother, Amanda Sterling, acknowledged that her daughter had been having behavioral issues for the last few years. However, she said nothing could have prepared her for this.

"You take away things from kids, you know electronics, or what have you. They get mad and they act out,” Sterling's attorney Alex Manning said. “No one could have predicted this."

Sterling told 11Alive that Cassandra, or Cassie as she was known among family, had become so out of control in the past year and a half that she relinquished custody of her daughter and handed it over to the Bjorges. Cassie had been living at her grandparents’ home before the gruesome killing.

But the behavioral trouble didn’t end when Cassie moved in with her grandparents. Gwinnett Police said that between October 2015 and March 2017 they responded to the victims' Lawrenceville home 31 times for various reasons – 18 of those times on runaway calls. Several of those calls were domestic dispute calls and illegal drug suspicion calls. The teen was even previously charged for allegedly assaulting her grandmother.

But despite everything, the mother said she never imagined things would end up like this.

“This was very unexpected,” Sterlind said. “Not in a million years did I think something like this would ever happen."

Police are still investigating the incident and said they have reason to believe that after the murders, teens other than Bjorge and Rider may have been inside the home. Police said the other teens were not related to the actual deaths, but may have information proving critical to the ongoing investigation.

Police said they are asking parents in the area to talk to their teens to see if they were in the house or had contact with the suspects between April 1 and April 8. If so, investigators would like to speak with them.