Police say one of two brothers accused of drugging and beating their parents had been planning the attack since he was 11 years old.

Authorities say 22-year-old Christopher Ervin and 17-year-old Cameron Ervin face charges including aggravated assault after the Sept. 5 attack in the family's suburban Atlanta home.

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

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

Their parents, Yvonne and Zachary Ervin, both 50, were hospitalized but survived. Yvonne Ervin had told a 911 dispatcher during the attack that her sons were trying to kill her.

Lawyers for the brothers didn't immediately return messages seeking comment Thursday.