A man accused of killing nearly two dozen older women and who was convicted last year in the slayings of two was killed Tuesday morning by his cellmate at a Texas prison, an official said.

Billy Chemirmir, 50, was found dead in his cell, said Texas Department of Criminal Justice spokeswoman Hannah Haney. She said that Chemirmir’s cellmate, who is serving a sentence for murder, was identified as the assailant, but said she couldn’t release the cellmate’s identity or how Chemirmir was killed.

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Authorities said Chemirmir preyed on older women in the Dallas area over a two-year span, killing them and stealing their valuables. He was caught after a 91-year-old woman survived an attack in 2018 and told police Chemirmir had forced his way into her apartment at an independent living community for seniors, tried to smother her with a pillow and took her jewelry.

Police said they found Chemirmir the following day in the parking lot of his apartment complex holding jewelry and cash, having just thrown away a large red jewelry box. Documents in the jewelry box led them to the home of Lu Thi Harris, 81, who was found dead in her bedroom.

The first capital murder trial of Chemirmir for the slaying of Harris ended in mistrial in Dallas County. He was later convicted in a second trial for Harris’ death and then convicted of a second killing in the death of Mary Brooks, 87.

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Following his second conviction, family members of those Chemirmir was accused of killing gathered at a Dallas courthouse to face him. In Ellen French House’s victim impact statement, she told Chemirmir, who was wearing a striped jail uniform, that she wanted him to see two photos of her mother: one of Norma French alive, the other after the 85-year-old was killed.

“This is my beautiful mother,” House said as she displayed the first photo. “This is my mother after you pried her wedding ring off of her finger that she couldn’t even get off.”

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Chemirmir had been indicted on 22 capital murder charges. Thirteen of the charges were in Dallas County while nine were in Collin County. Collin County prosecutors said last month that after the two convictions in Dallas County, they would not seek the death penalty in their cases.

Chemirmir, who maintained his innocence, was serving two sentences of life without the possibility of parole. He was imprisoned at the Coffield Unit in Tennessee Colony, located about 100 miles southeast of Dallas.

Haney said that the Office of Inspector General is investigating his death.