Patterson was charged in February with murder for the October 15 shooting deaths of Closs' parents in Barron, Wisconsin, and for kidnapping the girl he is alleged to have targeted seemingly at random after spotting her boarding a school bus. According to a police complaint, he then kidnapped Jayme and kept her captive at his cabin, about 65 miles to the north, for almost three months - until she escaped on January 10. Barron County Sheriff Chris Fitzgerald said he was aware Patterson had sent a letter to Raguse, KARE reported.
Asked whether he has any remorse or regrets for his actions, Patterson replied: "Huge amounts".
Greg O'Meara, a former Milwaukee County prosecutor who worked on the case against serial killer Jeffrey Dahmer, who tried and failed to use the insanity defense, said that Patterson didn't appear to be insane.
On the back of the letter, according to an image posted by KARE 11 News, are large bubble letters: "I'm Sorry Jayme!"
"I knew when I was caught (which I thought would happen a lot sooner) I wouldn't fight anything".
Wisconsin authorities have told the news station they believe the letter, postmarked February 28, is authentic.
The teen's family said police told them about the letter but declined to offer further comment, according to KARE-TV.
Patterson's attorneys did not immediately respond to messages from AP. He is being held on $5 million bail pending a March 27 arraignment, where he's expected to enter his plea.
Last month, Closs' friends told CBS News' Jamie Yuccas the girl has been making steady progress dealing with her trauma. "Don't want them to worry about a trial".
Before his arrest, Patterson was not on police's radar, they said.
"My brother... got a puppy named "Vale" a couple of weeks before [heart] Jayme [heart] ran away", Patterson wrote in the letter.
Though he didn't detail what triggered him to launch the killing spree he said he was "really pissed" at the time.
Thompson said it's impossible that Patterson didn't plan the murder and kidnapping. "These words come directly from my heart and my family's heart". "I tried to give them everything ... so they didn't have to interview Jayme". Jayme hides on Sat. [PEN SCRIBBLE REDACTION] My family respects privacy so no one even went in my room.
While he was allegedly holding Jayme hostage, the letter says, the suspect followed news updates on the kidnapping on his phone but would change the channel if it appeared on television. Can't express it. I'm Sorry Jayme!