We're getting a closer look inside the home of Jon and Marion Setzer, the Wilson County couple killed by a powerful explosion.
Their son-in-law, Richard Parker, is charged with their murders.
And even though the explosion left the home in shambles, a top bombing expert says he can tell a lot of clues from the wreckage.
Investigators carefully combed through the house, spending days collecting and testing evidence. But just with what is left behind, Jim Cavanaugh, a retired ATF special agent in charge, said experts can tell what the bomb was made of, how and where it exploded and even possible motives for the murders.
"The bomber believes that the evidence will be destroyed. Most of us believe that the evidence will be destroyed. But, in reality, the evidence just changes state," Cavanaugh said.
Looking at the aftermath inside the Setzers' home, Cavanaugh quickly deduces a lot.
"It's powerful, but it's easily contained in a small device," he said.
The explosive was hidden in a lamp, according to sources close to the investigation.
With that, Cavanaugh shows the likely placement of the homemade bomb.
"The hole in the ceiling would indicate that that is directly below the seat of the blast, and most likely, if that was a lamp, is the bass plate. And it would shoot straight up," Cavanaugh said.
Investigators also know possible and plausible motives.
"In this case, with a family member, I'm certainly probably looking at motives that would surround greed and revenge," Cavanaugh said.
It's clear the Setzers, not suspecting an explosion, detonated a device designed to kill and built with careful premeditation.
"Just think about a bomber over his device in his work bench, connecting the wires, making the switches, fitting the explosives inside," Cavanaugh said. "It's a very planned, methodical, diabolical crime."
Cavanaugh says, typically, bombers like to view their crimes from a distance, and they almost always intend to get away without getting caught.
"Because they want to reap the benefits of the crime," Cavanaugh said.
But based on what this killer left behind, Cavanaugh says that likely never would have happened.
"You don't get away with bombings. Eric Rudolph, the Unibomber, Timothy McVay, you can go down the list," Cavanaugh said. "Usually the bomber is not quite as good as they think they are."
Investigators say a murder involving a bullet or a knife likely means the suspect is dealing with the local law enforcement. But in the case of a bomb, like this one, and all of a sudden the ATF, FBI, Tennessee Bureau of Investigation, Tennessee Bomb and Arson, police and deputies all get involved.
The likelihood of getting caught increases significantly, and so do the severity of the charges. Life in prison or even the death penalty could be possible in this case with a conviction.
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