SNELLVILLE, Ga. (AP) — One of two brothers accused of drugging and beating their parents had been planning the attack since he was 11 years old, police say in court documents.

Christopher Ervin, 22, and Cameron Ervin, 17, face charges including aggravated assault and arson after the Sept. 5 attack in the family's suburban Atlanta home.

A search warrant document states that one suspect told police he'd been planning the attack since age 11, The Atlanta Journal-Constitution reported (http://on-ajc.com/1izqZjP ).

The warrant doesn't specify which of the brothers police were referring to in the documents, WXIA-TV reported (http://on.11alive.com/1ijv37d ).

Their parents, Yvonne and Zachary Ervin, both 50, were hospitalized but survived.

Yvonne Ervin told a 911 dispatcher during the attack that her sons were trying to kill her. She said her sons had drugged her and her husband by putting Xanax in their drinks before the attack, she told the 911 operator.

When officers arrived, they found a bloody scene inside the family's home, and Zachary Ervin emerged from the garage covered in blood, Gwinnett County police said.

The brothers had also turned on the gas to the fireplace and lit a candle in a failed attempt to blow up the house, Gwinnett County District Attorney Danny Porter has said.

The parents told police their sons also tried to strangle them, and Yvonne Ervin said that what she believed was a flammable liquid had been poured on her, WXIA reported.

In addition to the assault charges, both men are charged with first-degree arson, Gwinnett County Detention Center records show.

Lawyers for the brothers didn't immediately return messages from The Associated Press seeking comment Thursday.