Hoffman, 30, is serving life in prison without parole after pleading guilty last month in the deaths of Tina Herrmann, her 11-year-old son, Kody Maynard, and her neighbor Stephanie Sprang.
Prosecutors told him they wouldn't seek the death penalty if he revealed where the bodies were and explained in detail what happened.
Most of the four-page confession focuses on four days Hoffman spent at his Mount Vernon home with the kidnapped girl, whom he also pleaded guilty to raping. You can read a portion of the confession below.
He said he cooked her hamburgers, let her play video games and slept with his arm around her, the newspaper said.
He also described how he bound the girl's hands and feet and promised the girl, a relative of Herrmann's, she'd soon be home with her family. The girl was found alive, bound and gagged, on a bed made of tree leaves in his basement.
Hoffman is essentially an unremorseful, calculating criminal, prosecutors said.
"His perception of himself is self-serving, and he may very well believe he treated her like a houseguest, but she was a kidnap victim," Knox County prosecutor John Thatcher said. Thatcher called the confession "a really odd, strange, disturbing window into the mind of someone who can treat a child like this and still portray himself as the perfect host."
Hoffman confessed that Herrmann's house was a random target, picked because no neighbors were close and the garage door was left slightly open, and he said he staked out the house and slept in the woods across from it on the night before the killings, the newspaper reported.
He slipped in under the garage door after Herrmann and the other people left, spent an hour in the home and then killed Herrmann and Sprang in a panic when they returned.
"At this time I was in a total state of shock," he said. "I wandered around the house slowly coming to the realization of what I had done and how bad it was."
When the children entered the house, he killed the boy, and the girl ran to another room, he said.
He dismembered the three bodies - what he called "processing" - and by the next day, a Thursday, he'd used his tree-climbing equipment to make a pulley system to drop the bodies into a hollow, 60-foot tree.
That day, several days before authorities found Hoffman and the girl at his home, unsuspecting deputies approached Hoffman as he sat in a parking lot where officials had just found Herrmann's pickup truck. Hoffman told them he was waiting for his girlfriend to get off work, then drove home.
Authorities raided his home the following Sunday morning as he slept on a couch, and they found the girl.
Hoffman said in his confession he had intended to let the girl go and was happy she was rescued.
"I would not have hurt her," he said. "I could not hurt her."
Excerpts from Matthew Hoffman's confession letter:
I parked my car in Howard and walked from there to the house. I got to the woods across the street from the house a little after midnight. I slept across the street from the house that night in a sleeping bag. I woke up at daylight. There were two vehicles parked at the house during the night, and I saw that the gray car had left. I went back to sleep until around nine on Wednesday morning. I stayed there until a woman left in a pickup truck. This meant that there were no vehicles at the house. I walked across the street and tried to enter the front door, but it was locked. I then went in through the garage door. The garage door was not closed all the way so I slid under it into the garage. I kicked the door into the house from the garage. By this time it was approximately 10:30 AM Wednesday morning.
I looked around the house to make sure that no one was there. Even if I did not take anything, there was a certain amount of excitement in being in someone else's home without them being there. I was looking for anything of any real value. I was getting ready to leave as I had been there approximately an hour, but someone pulled into the driveway. I was back in the bedrooms when she entered the house and was unable to exit without breaking a window and trying to jump out. I had my knife for a certain amount of intimidation in case I ran into someone and needed to make an escape.
I made her breakfast, and at this time (surviving victim) was asking me a lot of questions. I told her that everything was fine, and it was going to be fine. I was getting extremely tired, but I did not think that I could sleep. I set up a movie and we watched (Iron Man I and II) them during the say. I wanted to sleep, but did not get very good sleep for fear of her leaving. I did not want to keep her tied up at all times so I let her be free at this time. I slept a little with my arm around here, and did this to ensure she would not leave, while at the same time, not having to tie her up.
The Associated Press/WKYC-TV