A man convicted of killing two elderly women and suspected of killing more than a dozen others died Tuesday in his cell at a state prison in East Texas, according to multiple reports.

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Billy Chemirmir, 50, was killed by his cellmate at the H.H. Coffield Unit in Tennessee Colony, Texas Department of Criminal Justice spokeswoman Hannah Haney told The Dallas Morning News. The name of Chemirmir’s cellmate, who was serving a sentence for a murder in Dallas County, was not immediately released.

Authorities are investigating.

At the time of his death, Chemirmir was serving two life sentences without parole for a pair of capital murder convictions in Dallas County, KETK reported.

Last year, a jury found Chemirmir guilty of smothering Lu Thi Harris, 81, to death in 2018. His conviction came a year after a separate jury considering the case deadlocked.

In October 2022, a jury convicted Chemirmir of another capital murder charge in the 2018 death of Mary Brooks, 87, KXAS-TV reported.

He had also been indicted on 20 other capital murder charges, according to the Morning News. He maintained his innocence through his court proceedings, telling the newspaper that he was “not a killer” and that he “didn’t have any problems all my life.”

Authorities said that over a two-year period beginning in 2016, Chemirmir killed 22 elderly women. He targeted women in their homes and at senior independent living centers, using pillows to smother them to death before stealing their jewelry, prosecutors said, according to KXAS.

Previously, Chemirmir was a senior-living caregiver, the Morning News reported.