FORT WORTH, TX) — A Fort Worth man jailed last month on a charge of assaulting an elderly man now stands accused of killing one of Tarrant County’s most notorious accused child molesters inside the jail.

The Fort Worth Star Telegram reports David Faustino Flores has been charged with the murder of 76-year-old Clinton Don Simpson of Keller, accused in 2007 of molesting 12 children at “Mr. Don’s Whistle Stop,” a miniature train station and track, owned and operated by Simpson in his backyard.  Simpson had been in state hospitals for years because he was found incompetent to stand trial.  He was found dead at the Tarrant County Jail on Wednesday from blunt force trauma.

Texas Rangers are leading the investigation.