Clackamas County Sheriff’s OfficeAdrian Wallace

A family dispute appears to be at the heart of a Monday double homicide in Lake Oswego, according to new information released Tuesday from the Clackamas County Sheriff’s Office.

Adrien Graham Wallace, 41, will be arraigned on two counts of aggravated murder at 3 p.m. today for allegedly killing his 71-year-old mother and 16-year-old nephew. They were shot slightly after 6 p.m. at a home just outside Lake Oswego city limits, in the 18000 block of Southwest Indian Springs Circle.

Saundra Sue Wallace, Adrien’s mother, lived in the house with her son before she was shot and killed Monday, according to law enforcement information. Officials did not have information about whether Nicholas Brian Juarez, the teenager who was also shot and killed, lived in the same home, or whether he lived elsewhere.

This story originally appeared on Oregon Public Broadcasting.