Investigators said that Matthew Hoffman targeted Tina Herrmann's Howard, Ohio, home because he knew her garage door was broken.
Detectives told 10TV's Maureen Kocot that the breaking and entering that led to the slayings of three people on Nov. 10, 2010 was not the first time he broke into someone's home.
"He got excited doing burglaries because he was in other people's houses without them knowing it," said Agent Joe Dietz, of the Ohio Bureau of Criminal Identification and Investigation.
"He was getting turned on by it.," Dietz said. "He was excited by it. He used the word excited."
Hoffman snuck into Herrmann's house armed with a large hunting knife and slapstick.
"Whether he planned to kill anyone that day, for sure, I don't really know," said Knox County prosecutor John Thatcher. "What I do know is he didn't hesitate. It didn't take him more than a second to go from somebody who wants to kill, to somebody who kills."
Hoffman admitted to the slayings of Herrmann; her son, Kody Maynard; and a close friend, Stephanie Sprang. He also said he dismembered their bodies and hid them inside a hollow tree.
"I think he knew where that tree was, and he thought this will be where I hide the bodies when I finally do it," Thatcher said.
SWAT officers rescued 13-year old Sarah Maynard -- the only survivor -- from a dark crawl space in Hoffman's basement. He had held her captive for four days.
We may never know why Hoffman spared Sarah's life, but the horrific crime forced Knox County prosecutor John C. Thatcher to make the most difficult decision of his career, whether the state should spare Hoffman's life in exchange for the location of the victim's bodies.
"Some say you've got to try to make this deal if you can," Thatcher said. "I know one says don't do it."
After Maynard was found alive, Thatcher called a meeting with the families.
"I told them, 'Ultimately this is my decision and I take the responsibility on my shoulders,'" Thatcher said. "If people don't like it, they can blame me."
The families decided unanimously to make the deal. Hoffman lives in exchange for the location of the bodies, Kocot reported.
Hoffman is serving life in prison with no chance of parole. Investigators said he remains in protective custody and is shielded from the other inmates.
Hoffman declined all media interviews but he agreed to see Knox County Sheriff David Barber.
"He was more interested in me showing him pictures of the tree than really talking about why he did what he did," Barber said.
Hoffman also allowed Dietz to visit him - once -- and talked about the need to heal.
Hoffman's mother said that she talks to her son every week on the phone and visits him every few months in prison.
She read a part of his confession letter to 10TV's Ashleigh Barry.
"I did not enter the house to kill those people. I did not know a single one of them," the letter said. "I did not plan for any of this to happen, I did not want to kill anyone."
Hoffman has given investigators little insight into the mind of a killer.
Investigators may never get the answers to their questions but some believe Hoffman was on his way to becoming a serial killer.
"Next time he goes out to try and get excited by a crime a burglary's not going to do it,
Dietz said. "Potentially, it might have been a serial killer in the making and that might have been his first event."
Thatcher said that the community can rest assured that Hoffman will never live outside prison.
"There's no way Matthew Hoffman is ever going to get out of prison and be in society again," Thatcher said. "That can't happen."
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