A 14-year-old girl whose 18-year-old boyfriend is accused of killing her parents left with him willingly after the slayings, prosecutors said in court papers filed Monday.

David Ludwig told detectives Kara Borden ran from her home and into his car after he shot her parents Nov. 13, and Borden said she went with him of her own free will, according to documents filed by Lancaster County prosecutors. They said kidnapping charges against Ludwig would be dropped.

Ludwig confessed to the killings, saying he shot the parents after the father told him to stop seeing his daughter, according to the filing. Ludwig said he shot Michael Borden in the back as he was going down the hallway to the front door and then headed toward Cathryn Borden.

"I shot mom as she was sitting in the chair," Ludwig was quoted as saying. "It was an intentional murder, I intended to shoot them, and I did."

Ludwig told detectives that after the killings, he couldn't find Kara Borden. He said he started to drive away and saw her running down the road toward him.

She got in the car and said she wanted to "get as far away as possible, get married, and start a new life," Ludwig told detectives.

District Attorney Donald Totaro said the kidnapping charge against Ludwig, of Lititz, will be dropped at his preliminary hearing next month.

Robert Beyer, an attorney representing Kara Borden, said he was not upset by the news that the kidnapping charge would be dropped.

Investigators have said they are treating Kara Borden as a crime victim but that the investigation is continuing.

Police caught up to Ludwig and Borden the day after the killings following a chase that ended with him crashing his parents' car into a tree in Belleville, Ind.

Earlier Monday, Indiana authorities released a search warrant affidavit for the car the couple drove nearly 600 miles from the murder scene in central Pennsylvania to Indiana.

Ludwig told Indiana State Police that a Glock semiautomatic pistol he used to kill the Bordens was under the driver's front seat of the car, according to the affidavit.

Police seized a .40-caliber Glock pistol and a .223-caliber rifle under a search warrant executed Wednesday.

Ludwig is being held without bail, awaiting a Dec. 16 preliminary hearing on murder charges.

In a signed statement he gave to Pennsylvania authorities, Ludwig said he went to the Borden home armed with several weapons. After Kara's father and Ludwig talked for 30 to 45 minutes, Michael Borden told the teen he could no longer see Kara.

"Ludwig said that's why he decided to shoot her dad and her mom," detectives said in the court papers.

James Gratton, a public defender representing Ludwig, said he was aware that Ludwig had given a statement to Indiana authorities, but did not know specifically what he told them.

In a court filing Friday, Ludwig's attorneys said they wanted investigators to preserve evidence in Ludwig's wallet, such as receipts from their journey, so that surveillance video could be obtained. They said the video would show he didn't kidnap the girl.