Lt. Gen. Suwat Tumrongsiskul, head of Thailand's immigration police, said he was not present for the questioning, which was conducted by U.S. law enforcement officials. But according to what he was told of the interrogation, the 41-year-old suspect,, "said he drugged the child," according to the Thai officer.
He added that Karr said he had then had sex with the child, and that she was still alive at that point. But he said the suspect said he then realized he had "accidentally" killed her.
An autopsy said a blood screening showed no drugs or alcohol in the child's body but said she had vaginal abrasions.
Karr has not yet been formally charged, Boulder, Colo., district attorney Mary Lacy said in a news conference Thursday, adding that there is "much more work" to be done in the case. She warned the public not to "jump to conclusions," and suggested that the arrest may have been forced by other circumstances, including the need for public safety and fear that Karr might flee.
Karr will be taken within the week to Colorado, where he will face charges of first-degree murder, kidnapping and child sexual assault, Ann Hurst of the Department of Homeland Security told a news conference in Bangkok. Karr was given a mouth-swab DNA test in Bangkok, according to a law enforcement official, and will be given another DNA test when he returns to the United States, the official said.
"I was with JonBenet when she died," Karr told reporters Thursday, visibly nervous and stuttering as he spoke. "Her death was an accident."
Asked if he was innocent of the crime, Karr said: "No."
However, the suspect's ex-wife, Lara Karr, who divorced him in 2001, told KGO-TV in San Francisco that during Christmas season of 1996, when JonBenet Ramsey was strangled and beaten to death in Colorado, she and her then-husband were living in Alabama — and that she was with him the entire Christmas season.
No evidence against John Karr has been made public beyond his own admission. U.S. and Thai officials did not directly answer a question at the news conference Thursday about whether there was DNA evidence connecting him to the crime.
As Karr was escorted to his guesthouse by U.S. and Thai authorities to pick up his belongings, he told the AP: "I am so very sorry for what happened to JonBenet. It's very important for me that everyone knows that I love her very much, that her death was unintentional, that it was an accident."
Asked what happened when JonBenet died, he said: "It would take several hours to describe that. It's a very involved series of events that would involve a lot of time. It's very painful for me to talk about it."
Dressed in a baggy turquoise polo shirt and khaki pants, Karr said that JonBenet's death was "not what it seems to be," though he declined to elaborate. "In every way," he added, as authorities bundled him into a waiting vehicle, "it's not at all what it seems to be."
An investigation that seemed to go nowhere, combined with lurid details and striking videos of the girl coquettishly performing in child pageants, propelled the case into one of the highest-profile mysteries in the United States.
Some feared the case would never be solved — and as investigators failed to produce suspects, some suspicion fell on the girl's parents, John Ramsey and his wife, Patsy, who died of ovarian cancer in June.
Lin Wood, the Ramsey family's longtime attorney in Atlanta, said that Karr had sent numerous e-mails in recent months making statements about the murder to a professor at the University of Colorado at Boulder. A source described the e-mails to CBS News as "hair-raising — to see what he'd done, or contemplated doing, to children."
Karr had been in Thailand five times over the past two years, arriving most recently in Bangkok on June 6 from Penang, Malaysia, Suwat said. He was looking for a teaching job in Thailand, Thai police official Lt. Gen. Suwat Tumrongsiskul Suwat said.
Suwat told reporters that Karr insisted his crime was not first-degree murder.
"He said it was second-degree murder. He said it was unintentional," Suwat said. He said Karr told Thai interrogators that he picked up JonBenet at her school and brought her to the basement. "He said he loved this child, that he was in love her. He said she was very pretty, a pageant queen. She was the school star, she was very cute and sweet."
The Thai officer quoted the suspect as saying he tried to kidnap JonBenet for a $118,000 ransom but that his plan went awry and he strangled her to death.
Mickey Sherman, a defense attorney and CBS News legal consultant, said physical evidence, like the suspect's DNA, will be the linchpin in the case. "Because if that's not there, (Karr) could be nothing more than a crackpot injecting himself into this case," Sherman said. "I think they need more than him saying they need to be involved."
Karr's ex-wife said he often spent time reading up on the cases of Ramsey and Petaluma resident Polly Klaas, who was abducted and slain in 1993. She also said she does not believe that her husband committed the crime.
His father told The Denver Post that while Karr was in college as an adult, a professor encouraged him to write a book about the Ramsey case after being impressed with a school paper.
"He researched everything he could about her," Wexford Karr said.
Hurst said Karr, who had traveled extensively across the world, may also be connected to a prior case in California's Santa Rosa County. She did not provide further details.
Asked how long he had been a suspect, she said, "A long time. I can't say specifically."
Hurst, with the Homeland Security's Immigration and Customs Enforcement in Bangkok, said Karr had left the United States several years ago and had not returned.
Karr claimed to have a succession of teaching assignments in online resumes purportedly posted to seek work abroad giving English lessons. But the resume makes no mention of Boulder, Colo., or California, where he has been wanted since 2001 for possessing child pornography, CBS News correspondent Kelly Cobiella reports.
A Wilson Elementary School official outside Petaluma, Calif. told KGO-TV that he twice hired Karr as a substitute in second- and fourth-grade classes in 2001. After observing him, Bob Raines says, he concluded Karr hadn't been trained, had poor skills keeping classes focused and was ineffective.
Karr applied for a teaching position in Bangkok two days ago.
The resumes of a "John Karr" are posted on at least two Web sites, based in South Korea and Los Angeles, along with a picture of a man who strongly resembles the man who appeared before reporters Thursday in Bangkok.
The resumes suggest that Karr traveled the globe teaching as a private tutor and at schools in Europe, Asia and Latin America over the past several years — though none of the positions that he claimed to hold could be immediately verified.
One resume claims Karr was employed "in some of the most prestigious schools in the United States, working with children from high-profile families" between 1996, the year JonBenet was killed, and 2001.
While in Germany working for a family with girls, ages 5 and 8, and a 10-year-old boy, the posting says Karr helped with homework and played outside with the children.
"I made sure the children had their evening bath, then put them to bed and read to them before they went to sleep," the resume says.
Suwat said U.S. authorities informed Thai police on Aug. 11 that an arrest warrant had been issued for Karr on charges of premeditated murder.
Police said Karr had been living in a dormitory-style hotel called The Blooms in a Bangkok neighborhood of massage parlors and travel agents that cater to expatriate residents and sex tourists.
The Ramseys learned that police were investigating Karr at least a month before Patsy Ramsey's death in June, the family said. Patsy's sister, Pamela Paugh, told CBS News' The Early Show that the Ramseys "were kept well informed in private and in closed meetings about the investigation."
John Karr spoke with JonBenet's grandparents, but the Ramseys refused an interview, Wexford Karr said.
In a statement, John Ramsey said that his wife "would no doubt have been as pleased as I am with today's development almost 10 years after our daughter's murder."
Investigators said at one point that JonBenet's parents were under an "umbrella of suspicion" in the slaying, and some news accounts cast suspicion on JonBenet's older brother, Burke. But the Ramseys always insisted an intruder killed their daughter. A 2005 48 Hours report found thatthe parents as suspects and investigators were no longer focusing on the Ramsey family.
Over the years, some experts suggested that investigators had botched the case so thoroughly that it might never be solved.