Son Accused of Attacking Parents in Georgia May Have Been Scheming for Years, Police Say

— -- One of the two Georgia brothers accused of trying to kill their parents in a violent attack may have been planning the crime since childhood, according to authorities.

A woman called 911 Sept. 5, "stating her children were trying to kill her and her husband" at their home in Snellville, Georgia, the Gwinnett County Police Department said. "She stated that her husband was distracting them so she was able to call for help," the police said.

Both parents were hospitalized after the attack but have since been released.

With the brothers, Cameron Ervin, 17, and Christopher Ervin, 22, now in custody, a search warrant affidavit ABC News obtained from ABC affiliate WSB-TV in Atlanta has revealed chilling new details about the planning of the alleged attack -- from years before to the night before the incident.

During interviews, the sons "admitted to attempting to set the residence on fire, strangling their parents with a pillow and/or plastic bag, and stabbing the father. In addition, one of the males stated that [he] wanted to cover up the evidence by setting the house on fire," the document said.

A detective wrote in the search warrant affidavit that "one of the sons also stated that he had been planning this since he was eleven years old." The warrant doesn't identify which son.

The brothers are also accused of giving their parents drugs in cocktails the night before. The document said: "during the attack, one of the sons asked the parents if they enjoyed the Xanax cocktail last night."

The brothers also may have tried to burn their parents, based on what the woman told police. The document said the mother told police that "during the attack the sons poured an unknown substance on her and then she felt heat on the back of her leg."

Police seized items including lighters, flammable substances, weapons, plastic wrap, Xanax pills and a knife, according to the document.

The document also revealed how the mother noticed strange behavior from her sons the night before the attack. The boys allegedly offered to cook dinner for the family, which they didn't normally do.

Gwinnett County Police Department told ABC News today it has no comment regarding possible motives.

Cameron and Christopher Ervin have been charged with aggravated assault with a deadly weapon and arson in the first degree to endanger human life, the police told ABC News. Both brothers remain in the Gwinnett County Detention Center, according to Sheriff's Department records.

In Georgia, 17 is considered adult age for prosecution of criminal offenses.

The brothers' attorneys, Tom Clegg and Mark Yun, did not immediately respond to ABC News' request for comment.

The brothers waived their first appearance in court last Friday. They remain held in jail without bond.

"I hate to waive preliminary hearings because they are a golden opportunity to find out things about the case at the earliest possible time," Clegg told the court. "The reason I'm waiving is because of the media interest in this case."