Shawn Ryan Grell, who murdered his 2-year-old daughter Kristen Salem by setting her on fire in a desert near Mesa, Arizona, has died in prison 26 years after the crime.

Grell was convicted of first-degree murder in 1999 and sentenced to death, but the sentence was overturned in 2013 when it was found he had intellectual disabilities in line with a U.S. Supreme Court ruling.

The horrific killing involved Grell dousing his daughter in gasoline and setting her ablaze while she was asleep, a crime described by the Arizona Supreme Court as especially heinous and cruel.

The Arizona Department of Corrections confirmed Grell’s death at the Arizona Prison Complex, though the cause remains under investigation.