Person of Interest in Pennsylvania Missing Men Case Confesses to Murder, Feels 'Deep Remorse': Lawyer

The person of interest in the disappearance of four young Pennsylvania men has confessed to murdering them, a defense attorney told reporters Thursday evening.

Cosmo DiNardo, 20, feels “deep remorse” and is “very emotional," said Paul Lang, one of his lawyers.

Read: Person of Interest Arrested in Case of 4 Missing Pennsylvania Men

In exchange for his full confession, DiNardo will be spared the death penalty, Lang said.

A motive for the killings was not released. DiNardo has a history of mental illness and has previously been held against his will in a psychiatric facility, according to a probable cause affidavit filed by Bucks County police. 

Late Thursday, The Associated Press reported DiNardo killed the men because he felt cheated or threatened during drug transactions, according to an anonymous source with knowledge of his confession.

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

DiNardo said he killed the men after selling them marijuana and burned their bodies at his parent's farm, the wire service said.

As he was led out of a Bucks County courthouse in shackles earliler Thursday, DiNardo said "I'm sorry," to reporters who yelled questions at him.

The remains of 19-year-old Dean Finocchiaro were found Wednesday in a 12-foot grave on a sprawling farm owned by DiNardo’s family, authorities said. Other remains were also found there, and DiNardo told authorities where to find all of the bodies, his attorney said.

Social media erupted Thursday with photos of DiNardo apparently holding a gun, and allegations that he exhibited aggressive behavior and wrote disturbing online posts.

DiNardo's parents reportedly own a successful concrete and construction business. 

Jimi Tar Patrick, 19, has been missing since last Wednesday. Finocchiaro, Mark Sturgis, 22, and Tom Meo, 21, disappeared last Friday.

DiNardo has been arrested twice since the young men, who knew each other, vanished last week.

Read: Body Found in Mass Grave Identified as 1 of 4 Missing Pennsylvania Men 

On Monday, he was picked up on a weapons charge and held in lieu of $1 million bail. His parents posted his bond on Tuesday night.

He was back in custody Wednesday for allegedly trying to sell Meo’s car, prosecutors said.

On Thursday, his attorney said he confessed to killing the four men. Prosecutors did not immediately comment on what charges DiNardo may now face.

A phone message left Thursday night by InsideEdition.com with Lang's office was not returned.

Watch: Police Searching for 4 Young Men Who Went Missing Within Days of Each Other