Outside in a pit Simmons' own children had dug, Simmons' wife was found shot, his 6 children strangled.
Later they found Simmons' two toddler grandchildren, wrapped in trash bags, hidden in the trunks of cars. All had been murdered days before.
Sheriff Duvall says he was forever changed by what he saw but was glad justice was served when Simmons was convicted of murder in two separate trials and sentenced to death.
Simmons' Defense Attorney John Harris has spoken about the trial for the very first time. He says Simmons confided in him and told him about the family's poorly shielded secret.
Simmons was infatuated with his daughter and had fathered his own grandchild when the family lived in New Mexico. He and his family fled to Arkansas when authorities issued a warrant for incest.
By 1987, Simmons told Harris, he felt his family start to slip away, "I think he felt like, they are going to take him out, he's going to take them out first, i think that was his mind set."
Harris watched as Simmons went to the death chamber in 1990. Though he'd said all along he wanted to die, when the injection began, Harris says Simmons started writhing, "The only explanation I can find for that is that the lethal injection caused him excrutiating pain or he saw something on the other side of life that he didn't like."
But blame, Harris said, should be shared. Had authorities made an arrest, he says, Simmons would have shed no blood. 16 lives, and perhaps even Simmon's own possibly spared.