Cosmo DiNardo and Sean Kratz were both charged with the criminal homicide in the deaths of four missing Pennsylvania men Friday. Kratz and DiNardo are cousins, according to reports, and were charged with the deaths of Jimi Patrick, 19, Tom Meo, 21, Mark Sturgis, 22, and Dean Finocchiaro, 19, of Bucks County, Pennsylvania.

In an agreement with Bucks County District Attorney Matthew Weintraub, 20-year-old DiNardo confessed to the killings and revealed the locations of all four bodies. He named Kratz, also 20, as an accomplice. Authorities located the bodies of all four men on a 68-acre property belonging to DiNardo’s parents.

Read: Texts From Cosmo DiNardo About 4 Missing Pennsylvania Men Show Lack Of Concern

As for the motive, officials said it still remained unclear.

“I don’t know that,” Weintraub said. “And I’m not sure we’ll ever know.”

Other sources and DiNardo’s own confession revealed something akin to drug deals gone wrong. DiNardo admitted to killing Patrick after he didn’t have the $8,000 he agreed to pay for four pounds of marijuana. He similarly told detectives Kratz and he agreed to rob Finocchiaro while selling him marijuana. DiNardo also said he set up a “deal” with Meo and Sturgis before their deaths.

Asked why four marijuana deals led to the deaths of four young men, Weintraub said he had no answer.

“I’m not sure,” he said, “we could ever answer that question.”

Paul Lang, one of DiNardo’s defense attorneys, told reporters Thursday the motive for the murders would emerge in time.

An Associated Press report Thursday cited an unidentified source close to the case who said DiNardo felt “cheated or threatened” during the drug transactions.

“Every death was related to a purported drug transaction,” the anonymous source told the AP. “And at the end of each one there’s a killing.”

Prosecutors said DiNardo suffered from schizophrenia. When he was first arrested as a person of interest in the case, his lawyers argued that his mental health was being exploited. Acquaintances and friends told reporters that DiNardo had been involved in an ATV accident some seven months prior to the killings and that ever since, something had been “off” with him. DiNardo also had contact with police more than 30 times since 2011, a law enforcement source told ABC News.

Read: Who Is Cosmo DiNardo? Man Who Confessed In Pennsylvania Killings Spoke Of Murder

Another unidentified friend of DiNardo’s told the Philadelphia Inquirer Thursday that DiNardo had spoken of murder in the past.

“He’s told me and my friends, ‘Yeah, I’ve killed people before, I just haven’t been caught,’” the man said. “We literally were just like, ‘Yeah, all right Cosmo, sure you did.’ No one actually thinks someone’s capable of this.”

In addition to charges of criminal homicide, both men faced multiple counts of robbery, conspiracy and abuse of a corpse, according to court documents reviewed by ABC News. Both Kratz and DiNardo were arraigned Friday afternoon though neither posted bail. The men were scheduled for a preliminary hearing July 31.