(Reuters) - A mother in northeastern Oklahoma shot and killed her two grown sons while they slept, then killed herself, law enforcement officials said Sunday.

Rebecca Smith, 48, also known as Rebecca Brown, fatally shot her sons Levi Brown, 25, and Garrett Brown, 24, on Saturday morning while they slept in a Webbers Falls home they shared with her, according to the Muskogee County Sheriff's Department.

The woman left a suicide note, called her brother to tell him she was going to commit suicide and then killed herself, the sheriff's department said. Smith’s brother called 911 after the call and deputies responded, finding all three bodies.

The Tulsa World reported that law enforcement is investigating what may have led to the killings and said Smith was taking medication. (Reporting by Heidi Brandes in Oklahoma City; Editing by Larry King)