A teenager charged with her husband with killing a man they met through Craigslist has admitted the slaying and said she has killed more than 20 others across America.
Miranda Barbour, 19, said in a prison newspaper interview she wanted to plead guilty to killing Troy LaFerrara in November.
She also said she had killed at least 22 others from Alaska to North Carolina in the past six years as part of her involvement in a satanic cult.
"I feel it is time to get all of this out. I don't care if people believe me. I just want to get it out," Barbour said.
She had no remorse because she killed only "bad people".
Sunbury police chief Steve Mazzeo said investigators were aware of Barbour's claims and were "seriously concerned". They had contacted police in other jurisdictions.
The FBI said its Philadelphia division had been in contact with the Sunbury police and would offer any assistance requested.
Lawyers for Barbour and her husband, 22-year-old Elytte Barbour, have sought psychiatric evaluations for their clients.
Miranda Barbour's lawyer also asked a judge last week to toss out statements she made before she was charged. Public defender Ed Greco said Barbour wasn't afforded a lawyer despite repeated requests during two police interviews.
Barbour said in the interview she had wanted to plead guilty but that Greco had pleaded not guilty for her.
Prosecutors are seeking the death penalty for both defendants in LaFerrara's killing.
The petite Barbour told police she met the 125-kilogram victim after he responded to her Craigslist advert offering sex for US$100. She said she and her husband stabbed and strangled LaFerrara because "he said the wrong things". "I remember everything," Barbour said. "It is like watching a movie."
Prosecutors say the husband hid under a blanket in the back of the car when his wife picked up LaFerrara at a mall near Harrisburg, 80 kilometres south of Sunbury. Barbour said she would have let LaFerrara go but after telling him she was just 16, he said he wanted to proceed with their pay-for-sex arrangement.
"If he would have said no, that he wasn't going to go through with the arrangement, I would have let him go," she told the newspaper.
On her signal, her husband strangled LaFerrara with a cord while his wife stabbed him about 20 times, police say.
Elytte Barbour told investigators they committed the crime because they wanted to kill someone together, according to court papers. The couple had married in North Carolina and moved to Pennsylvania about three weeks earlier.
Miranda Barbour offered little detail on the murders she claimed to have participated in in Alaska, Texas, North Carolina and California.
"When I hit 22, I stopped counting," she said. "I can pinpoint on a map where you can find them."
Barbour said she was introduced to murder at 13, after suffering sexual abuse as a child by a man who had been a member of a satanic cult in Alaska.
"I would lure these people in," she said. "I studied them. I learned them and even became their friend. I did this to people who did bad things and didn't deserve to be here any more."
Additional reporting by Reuters, Agence France-Presse