A law enforcement team in northeast Oklahoma believes the prolific serial killer known as “BTK” may be responsible for several additional unsolved missing person and homicide cases. Now they’re hoping the public can help them identify barns and silos in Oklahoma, Kansas and Missouri that the self-proclaimed BTK killer Dennis Rader sketched in never-before-seen detailed drawings.

Last month, the Osage County Sheriff’s Office publicly confirmed it was investigating Rader as the “prime suspect” in a 1976 cold case in their jurisdiction and several other unsolved crimes across three states.

The investigators believe the killer may have buried 16-year-old Cynthia Dawn Kinney in a barn near the Kansas-Oklahoma border. Kinney was last seen at a laundromat in Pawhuska, Oklahoma, in 1976. Her body has never been found.