The man investigators called the mastermind behind the deadly 2012 southside home explosion died Tuesday morning.
Mark Leonard, 48, who was convicted of multiple counts of arson and murder, appears to have died of natural causes, Indiana Department of Correction spokesman Doug Garrison said.
Leonard died after being taken to an Indianapolis hospital. He had been placed on imminent death watch earlier this week, which is a term used for inmates who are extremely ill and will likely die within days, Garrison said.
The exact cause of death has not been confirmed, but autopsy is planned to be done today, according to the department of correction.
Leonard had been sentenced to life in prison at the Wabash Valley Correctional Facility after he was found guilty of multiple felonies in a jury trial. Prosecutors said Leonard was the mastermind behind an explosion in the Richmond Hill neighborhood that killed a Greenwood school teacher and her husband. Investigators said Leonard, his then-girlfriend and his half brother concocted a plan to blow up the house to collect $300,000 in insurance money.
They allowed the home to fill with natural gas, and when it ignited, it exploded, damaging or destroying 80 homes in the Richmond Hill neighborhood, just north of County Line Road. Jennifer and Dion Longworth, who lived next door, were killed. Jennifer Longworth was a teacher at Southwest Elementary School in Greenwood.
The November 2012 explosion was felt for miles.
Leonard had been sentenced to two life sentences without parole, plus another 70 years in prison on multiple felony convictions, according to the department of correction. He was also convicted of a charge of conspiracy to commit murder for trying to hire someone to kill a key witness in his case.\
A total of five people were charged, convicted and sentenced in the case.