WAXAHACHIE, Texas — The Texas Rangers are investigating the death of a Wayne McCollum Detention Center officer who was allegedly killed by an inmate, according to the sheriff’s office.

Ellis County Sheriff Brad Norman held a press conference about the incident Tuesday. According to the sheriff’s office, the deceased officer is 28-year-old Isaiah Bias. He worked there for over six years.

Norman said Bias has been involved with the sheriff’s office since he joined the sheriff’s explorers program when he was 14. The program is for young people between 14 and 21 who are interested in a law enforcement career.

The sheriff’s office said the incident happened Dec. 16 at approximately 3:45 p.m. Bias was returning 45-year-old Arron Semeion Thompson to his cell when Thompson attacked him.

Staff gave Bias first aid until paramedics transported him to Baylor Scott and White Medical Center in Waxahachie, where he was pronounced dead.

Thompson has been charged with capital murder and is being held on a $2 million bond. He has been transferred to a different facility.

“I can honestly say that my staff, over the last day, has dealt with pure evil. May God bless Isaiah’s family, friends and colleagues,” Norman said.

Thompson was initially in jail for three counts of assault of a public servant and an evading charge, and had been in jail since early November. He was in a segregated area and was in a cell for 23 hours a day. He was allowed to be out of his cell for one hour per day for recreation.

The incident occurred when Bias was putting him back in his cell after his recreation time.

Norman said it’s up to the Ellis County District Attorney’s Office as to whether Thompson faces the death penalty in the case.