A Missouri jail nurse who allegedly wanted to marry a man convicted of killing a lottery winner has been charged with poisoning her husband and setting their home on fire, according to court records.

Amy Murray, 40, is facing charges including first-degree murder and arson in the Dec. 11 death of her husband, Joshua Murray. Investigators said he was found dead in the master bedroom of the couple’s burned-out home in Iberia, and that his wife later told the prison inmate in a recorded phone call that they could get married because her husband was “out of the picture.”

An autopsy determined her husband was poisoned by a chemical in antifreeze and likely died before the blaze started.

Amy Murray remained jailed Monday on a $750,000 bond. Her attorney didn’t immediately return a phone message Monday seeking comment from The Associated Press.

Murray reported finding the home ablaze when she returned from taking the couple’s 11-year-old son and two dogs to a McDonald’s, a Miller County sheriff’s detective wrote in a probable cause statement released last week. She told investigators she couldn’t get inside the home because the house was filled with smoke.

But investigators said they found a McDonald’s sandwich on the kitchen counter at the house in Iberia, which is about 140 miles (about 225 kilometers) southeast of Kansas City.

Murray worked part-time as a nurse at the Jefferson City Correctional Facility, where she had a “romantic relationship” with inmate Eugene Claypool that had been ongoing “for some time,” according to authorities and charging documents. Claypool, who isn’t charged in the case, was sentenced to life in prison for fatally stabbing an elderly man in 2000.

In recorded phone calls at the facility, Murray told Claypool she wanted to divorce her husband. Following the fire, she allegedly told Claypool they could get married because her husband was dead and “out of the picture,” according to court documents. She and Claypool also discussed getting an attorney so Claypool could be released from prison early.

Claypool and another man pleaded guilty to killing 72-year-old Donald Hardwick, who was attacked in his home on Christmas Day in 2000. Hardwick, who couldn’t walk without using a walker, won a $1.7 million Missouri Lottery jackpot in 1998. Investigators said Claypool and his co-defendant targeted Hardwick believing he had $10,000 stashed in his Springfield home.

Investigators said Claypool repeatedly stabbed Hardwick, whose wife later found him dead with a Bible on his chest.