The Oklahoma State Bureau of Investigation is looking into a double stabbing that killed a woman and critically wounded her brother on Friday night, a news release says.
Betty Diane Evans, 51, died from stab wounds and her brother, Robert Evans, was flown by medical helicopter to a Tulsa hospital.
According to OSBI, Vernon Stanbrough, 62, was arrested on complaints of first-degree murder and assault and battery with a deadly weapon.
Stanbrough stabbed the siblings at Betty's home in the 500 block of East Washington Street in Bristow, according to OSBI.
The agency says it is still exploring the possible motive.
Stanbrough was last released from prison in 2011. He currently is serving a suspended sentence for drugs, pornography and assault with a deadly weapon convictions, Oklahoma Department of Corrections records show.