Cosmo DiNardo is escorted to a vehicle while in police custody Thursday, July 13, 2017, in Doylestown. Picture: Matt Rourke/AP
Cosmo DiNardo is escorted to a vehicle while in police custody Thursday, July 13, 2017, in Doylestown. Picture: Matt Rourke/AP
In this aerial photo, investigators work under tents as they search for clues in the disappearance of four men in Solebury. Picture: Michael Bryant/The Philadelphia Inquirer via AP
In this aerial photo, investigators work under tents as they search for clues in the disappearance of four men in Solebury. Picture: Michael Bryant/The Philadelphia Inquirer via AP
A law enforcement official escorts Cosmo DiNardo to a vehicle in Doylestown. Lawyer Paul Lang, a defense attorney for DiNardo, said his client has admitted killing the four men who went missing last week and told authorities the location of the bodies.  Picture: Matt Rourke/AP
A law enforcement official escorts Cosmo DiNardo to a vehicle in Doylestown. Lawyer Paul Lang, a defense attorney for DiNardo, said his client has admitted killing the four men who went missing last week and told authorities the location of the bodies. Picture: Matt Rourke/AP
A law enforcement official escorts Cosmo DiNardo to a vehicle Thursday, July 13, 2017, in Doylestown, Pa. Lawyer Paul Lang, a defense attorney for DiNardo, said Thursday that his client has admitted killing the four men who went missing last week and told authorities the location of the bodies. Lang says prosecutors agreed to take the death penalty off the table in return for DiNardo's cooperation. (AP Photo/Matt Rourke)
A law enforcement official escorts Cosmo DiNardo to a vehicle Thursday, July 13, 2017, in Doylestown, Pa. Lawyer Paul Lang, a defense attorney for DiNardo, said Thursday that his client has admitted killing the four men who went missing last week and told authorities the location of the bodies. Lang says prosecutors agreed to take the death penalty off the table in return for DiNardo's cooperation. (AP Photo/Matt Rourke)
A law enforcement official escorts Cosmo DiNardo to a vehicle Thursday, July 13, 2017, in Doylestown, Pa. Lawyer Paul Lang, a defense attorney for DiNardo, said Thursday that his client has admitted killing the four men who went missing last week and told authorities the location of the bodies. Lang says prosecutors agreed to take the death penalty off the table in return for DiNardo's cooperation. (AP Photo/Matt Rourke)
A law enforcement official escorts Cosmo DiNardo to a vehicle Thursday, July 13, 2017, in Doylestown, Pa. Lawyer Paul Lang, a defense attorney for DiNardo, said Thursday that his client has admitted killing the four men who went missing last week and told authorities the location of the bodies. Lang says prosecutors agreed to take the death penalty off the table in return for DiNardo's cooperation. (AP Photo/Matt Rourke)
A law enforcement official escorts Cosmo DiNardo to a vehicle Thursday, July 13, 2017, in Doylestown, Pa. Lawyer Paul Lang, a defense attorney for DiNardo, said Thursday that his client has admitted killing the four men who went missing last week and told authorities the location of the bodies. Lang says prosecutors agreed to take the death penalty off the table in return for DiNardo's cooperation. (AP Photo/Matt Rourke)
A law enforcement official escorts Cosmo DiNardo to a vehicle Thursday, July 13, 2017, in Doylestown, Pa. Lawyer Paul Lang, a defense attorney for DiNardo, said Thursday that his client has admitted killing the four men who went missing last week and told authorities the location of the bodies. Lang says prosecutors agreed to take the death penalty off the table in return for DiNardo's cooperation. (AP Photo/Matt Rourke)
Lawyer Paul Lang, a defense attorney for Cosmo DiNardo, said his client has admitted killing the four men who went missing last week and told authorities the location of the bodies. Lang says prosecutors agreed to take the death penalty off the table in return for DiNardo's cooperation. Picture: Matt Rourke/AP
Lawyer Paul Lang, a defense attorney for Cosmo DiNardo, said his client has admitted killing the four men who went missing last week and told authorities the location of the bodies. Lang says prosecutors agreed to take the death penalty off the table in return for DiNardo's cooperation. Picture: Matt Rourke/AP
A law enforcement official escorts Cosmo DiNardo to a vehicle  in Doylestown. Picture: Matt Rourke/AP
A law enforcement official escorts Cosmo DiNardo to a vehicle in Doylestown. Picture: Matt Rourke/AP
Antonio DiNardo the father of Cosmo DiNardo gets into a SUV to be driven away from a Bucks County government building in Doylestown. Picture: Matt Rourke/AP
Antonio DiNardo the father of Cosmo DiNardo gets into a SUV to be driven away from a Bucks County government building in Doylestown. Picture: Matt Rourke/AP
Fortunato Perri, a defense attorney for Cosmo DiNardo, walks to the Bucks County Courthouse. Picture: Matt Rourke/AP
Fortunato Perri, a defense attorney for Cosmo DiNardo, walks to the Bucks County Courthouse. Picture: Matt Rourke/AP
Defense lawyers Paul Lang, left, and Michael Parlow walk from the Bucks County Courthouse in, Doylestown, Pa., Thursday, July 13, 2017. Lang, a defense attorney for Cosmo DiNardo, said Thursday that his client has admitted killing the four men who went missing last week and told authorities the location of the bodies. Lang says prosecutors agreed to take the death penalty off the table in return for DiNardo's cooperation. (AP Photo/Matt Rourke)
Defense lawyers Paul Lang, left, and Michael Parlow walk from the Bucks County Courthouse in, Doylestown, Pa., Thursday, July 13, 2017. Lang, a defense attorney for Cosmo DiNardo, said Thursday that his client has admitted killing the four men who went missing last week and told authorities the location of the bodies. Lang says prosecutors agreed to take the death penalty off the table in return for DiNardo's cooperation. (AP Photo/Matt Rourke)
Bucks County District Attorney Matthew Weintraub said they've found human remains in their search for four missing young Pennsylvania men and they can now identify one victim. Picture: Clem Murray /The Philadelphia Inquirer via AP
Bucks County District Attorney Matthew Weintraub said they've found human remains in their search for four missing young Pennsylvania men and they can now identify one victim. Picture: Clem Murray /The Philadelphia Inquirer via AP

Doylestown, Pennsylvania - An admitted drug dealer with a history of mental illness was charged Friday with the killings of four Pennsylvania men who vanished a week ago. A second suspect was also arrested and charged in three of the deaths.

Cosmo DiNardo, 20, is charged with all four homicides and 20 other counts, including abuse of corpse, conspiracy and robbery, according to court documents. Sean Kratz, 20, faces 20 counts, including three of criminal homicide.

DiNardo's lawyer announced Thursday that his client had admitted to the killings and was cooperating with investigators. Kratz was arrested later the same day, authorities said.

All the victims are believed buried on a farm property in Solebury, Pennsylvania, owned by DiNardo's parents. Only one set of remains has so far been identified.

Pennsylvania State Police officers walk up a driveway in Solebury as the investigation of four missing young Pennsylvania men continues. Picture: Matt Rourke/AP

A person with firsthand knowledge of DiNardo's confession said he killed the men after he felt cheated or threatened during three drug transactions and then burned their bodies at his family's farm.

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, who was in custody.

This undated photo provided by Middletown Township Police Department shows Dean Finocchiaro. Investigators found the body of Finocchiaro, one of four missing young men, along with other human remains, buried deep in a common grave on a Pennsylvania farm. Picture: Courtesy of Middletown Township Police Department via AP

DiNardo told authorities that a co-conspirator from Philadelphia was involved in three of the deaths, the person said.

DiNardo has agreed to plead guilty to four first-degree murder counts, attorney Paul Lang said. In exchange for DiNardo's cooperation, Lang said, prosecutors would not seek the death penalty.

Lang called his client remorseful. As a law enforcement official escorted a shackled DiNardo from the courthouse on Thursday, he said "I'm sorry."

Kratz's mother, Vanessa, declined to comment on her son arrest's when reached by phone.

Bucks County District Attorney Matthew Weintraub, center, holds a press conference to announce that bodies have been found on a Solebury Township farm belonging to the DiNardo family, and have identified one victim as Dean Finocchiaro. Picture: Clem Murray /The Philadelphia Inquirer via AP

The Bucks County district attorney planned to hold a news conference Friday afternoon to report on all the latest developments.

The person with knowledge of the confession said one of the men was killed July 5 and the other three were killed July 7.

"Every death was related to a purported drug transaction, and at the end of each one there's a killing," the person said.

DiNardo 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.

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.

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, 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.

Associated Press