FORT WORTH, Texas — A Keller man accused in the molestation of 12 children died early Wednesday morning from injuries sustained in a beating while in custody in Tarrant County.

According to an affidavit and medical examiner's report, 76-year-old Clinton Don Simpson suffered blunt force injuries to the head when he was struck dozens of times by a fellow inmate.

David Faustino Flores, 42, was charged with Simpson's murder.

Flores was originally booked into the Tarrant County Jail that same morning after he struck an elderly man, according to records.

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David Faustino Flores
Tarrant County

At the time of the attack, Flores and Simpson were being housed inside the same cell in the medical unit of the Lon Evans Corrections Center. Since Flores was placed on a suicide watch, an officer was required to check the cell every 10 minutes.

According to records, an officer checked the cell at 2:15 a.m. Seven minutes later, the affidavit states, surveillance video showed Simpson in his wheelchair at the door of the cell, and it appeared he was yelling for help.

Authorities said an officer approached the cell and witnessed Flores hit Simpson in the head with a "closed fist." Video appeared to show Flores strike Simpson more than 60 times and then slam his head into the concrete floor.

Flores was then able to kick Simpson in the head several times before a sergeant could pull him out of the cell.

Simpson was transported to John Peter Smith Hospital, where he was pronounced dead at 3:09 a.m. Wednesday.

Prior to his arrest almost a decade ago, Simpson owned Mr. Don's Whistle Stop, a popular miniature train ride that he operated in his backyard for several decades. He was also a preacher at the Haslet Church of Christ.

In late 2007, he was indicted on nine counts of aggravated assault of a child and three counts of indecency with a child. The case involved 12 children ranging in age from 3 to 9 years old.

Nine of the children who came forward said they were assaulted on Simpson's miniature train. The other children alleged assaults took place in his home.

Authorities first initiated the investigation after parents of a 3-year-old girl went to police in October 2007. The parents told investigators that their daughter told them Simpson assaulted her on the train during a birthday party.

The investigation led to more accusations against the train operator, who police said admitted to fondling young girls on multiple occasions.

In 2009, Simpson was found incompetent to stand trial and resided in state hospitals over the years.

Per a sheriff's office request, the Texas Rangers are investigating Simpson's death.