An Oklahoma mother allegedly used a long gun to kill her two adult sons while they were sleeping Saturday morning before taking her own life, Muskogee County Sheriff’s officials told the Tulsa World.

Detectives believe the mother used a .22 rifle to fatally shoot her two sons and then to kill herself, Chief Deputy Brandon Caster told the paper. Prior to ending her life, he added, she left a suicide note.

The mother was identified by the paper as Rebecca Smith, 48, who also was known as Rebecca Brown. Her two sons were identified as Levi Brown, 25, and Garrett Brown, 24.

Smith also made a phone call to her brother and told him that she was going to commit suicide, Deputy Ashley Mullen told the Tulsa World.

The brother then called 911 and reported to dispatchers what his sister had told him, Mullen added. Deputies responded to the home shortly after 8a.m. to check on her welfare and discovered the three bodies.

Mullen told the paper the investigation into what may have prompted the mother’s actions remains open, including whether she suffered from mental-health issues.

“I know she had a lot of medications she was taking,” Mullen said.

The state medical examiner will perform an autopsy on all three bodies.