DOYLESTOWN, Pa. (AP) - A drug dealer has confessed to killing four young Pennsylvania men after he felt cheated or threatened during three drug transactions and then burned their bodies at his family's farm in suburban Philadelphia, a person with firsthand knowledge of his confession said.

The person spoke to The Associated Press on the condition of anonymity on Thursday because he was not authorized to publicly discuss details of the case against 20-year-old Cosmo DiNardo."Every death was related to a purported drug transaction, and at the end of each one there's a killing," the person said.DiNardo, 20, then burned the bodies - three of them inside a drum - at his family's farm in Solebury Township, about 30 miles (48 kilometers) north of Philadelphia, the person said, adding that a co-conspirator was involved in the deaths of three of the men.As a law enforcement official escorted a shackled DiNardo from the courthouse on Thursday, he said "I'm sorry.The person with knowledge of the confession said one of the men was killed July 5 and the other three were killed July 7.The details were provided after one of DiNardo's lawyers said Thursday that DiNardo had confessed to killing the missing men and told investigators where their bodies were located.DiNardo agreed to plead guilty to four first-degree murder counts, attorney Paul Lang said outside court, where DiNardo had met with investigators.In exchange for DiNardo's cooperation, Lang said, prosecutors would not seek the death penalty. The Bucks County District Attorney's Office had no response to the lawyer's comments on Thursday night. Authorities are expected to release additional information on the case Friday morning.Authorities had charged DiNardo earlier this year with having a gun despite an involuntary mental health commitment. In seeking $5 million bail on a stolen car charge this week, prosecutors said he had been diagnosed with schizophrenia. He also suffered a head injury in an ATV accident a year ago.DiNardo's parents declined to comment after leaving a government building where he spent several hours with the district attorney and other investigators.The victims are 19-year-old Dean Finocchiaro, 22-year-old Mark Sturgis, 21-year-old Tom Meo and 19-year-old Jimi Taro Patrick. Patrick, who was a year behind DiNardo at a Catholic high school for boys, was last seen on Wednesday, while the other three vanished two days later.Cadaver dogs led investigators this week to the spot on the family farm where they discovered human remains inside a 12 ½-foot-deep common grave. So far, investigators have only been able to identify one set of remains - those of Finocchiaro.