 -- Two 20-year-old men have been charged with multiple counts of homicide in the slayings of four young men in southeastern Pennsylvania, authorities said.

Cosmo DiNardo, of Bensalem, and Sean Kratz, of Philadelphia, were both charged with criminal homicide in the July 7 deaths of Dean Finocchiaro, 19, of Middletown Township, Thomas Meo, 21, of Plumstead Township, and Mark Sturgis, 22, of Pennsburg.

Investigators found the bodies of the three men Wednesday in a roughly 12-foot-deep grave on a sprawling property in Solebury Township owned by DiNardo's parents, according to the Bucks County District Attorney's Office.

DiNardo is also accused of killing Jimi Tar Patrick, 19, of Newtown Township, July 5, and burying him in a single grave elsewhere on the same property. DiNardo told detectives he used a backhoe to dig both graves.

DiNardo and Kratz have each provided statements to investigators, and DiNardo has described Kratz as his cousin, according to the district attorney's office.

Court documents obtained by ABC News show both men also face multiple counts of conspiracy, robbery and abuse of a corpse.

DiNardo and Kratz were arraigned Friday afternoon before Magisterial District Judge Maggie Snow of Buckingham Township. Neither were able to post bail. They are scheduled for a July 31 preliminary hearing before Snow, the District Attorney's Office announced Friday night.

At a news conference earlier Friday afternoon, Bucks County District Attorney Matthew Weintraub said he made an "agreement" with DiNardo that allowed investigators to locate Patrick's body, which was buried as far as a half-mile away from where the three other bodies were found. The agreement includes not seeking the death penalty, Weintraub said.

Patrick went missing July 5, while Finocchiaro, Meo and Sturgis all disappeared July 7.

All four men were shot and each victim has been positively identified. Their family members were briefed on details of the case Friday morning, according to the district attorney's office.

When asked about a motive, Weintraub said, "I don't know that and I'm not sure we'll ever know."

According to court documents, here is an account of what happened:

DiNardo told detectives he had agreed to sell Patrick four pounds of marijuana for $8,000. DiNardo said he picked up Patrick at the man's home in Newtown on July 5 and drove him to the DiNardo family's property in Solebury Township.

DiNardo told investigators Patrick only had $800 so he instead agreed to sell the man a shotgun for that amount. They then walked to a remote part of the property where DiNardo said he fatally shot Patrick with a .22-caliber rifle. DiNardo said he then drove a backhoe that was on the property to where Patrick lay, dug a hole no more than 6 feet deep and buried his body, according to the court documents.

DiNardo also told detectives he agreed to sell Finocchiaro a quarter-pound of marijuana for about $700 on July 7. DiNardo said he picked up Kratz and drove to Finocchiaro's home in Middletown, agreeing on the way there that they would rob the man. DiNardo said he handed Kratz a .357 handgun that belongs to his mother, according to the court documents.

DiNardo told investigators he drove Kratz and Finocchiaro to his family's property in Solebury Township, where he said Kratz shot Finocchiaro in the head as they were leaving a barn on the land. DiNardo said he then took the gun and shot Finocchiaro a second time while the victim was lying face down on the ground but claimed the man was already dead, according to the court documents.

DiNardo told detectives he wrapped Finocchiaro's body in a blue tarp and used the backhoe to remove him from the barn before placing the body into a metal tank, which he referred to as the "pig roaster," according to the court documents.

That same night, DiNardo said, he met Meo and Sturgis together at a parking lot in Peddlers Village. DiNardo told investigators he had a "deal" set up with Meo. DiNardo told investigators he directed Meo and Sturgis to follow him to the Solebury Township property and told Meo to park his car there. DiNardo then drove Meo and Sturgis to an adjacent property where Kratz was waiting, according to the court documents.

After Meo and Sturgis exited his vehicle, DiNardo said he shot Meo in the back with the .357 handgun. Meo fell to the ground and was screaming, he said. DiNardo told detectives he then fired several times at Sturgis as the man attempted to flee. Sturgis was struck and also fell to the ground. DiNardo said he had run out of ammunition, so he ran over Meo with the backhoe. He then used the machine to lift both bodies into the metal tank where he had already placed Finocchiaro's corpse, according to the court documents.

The next day, DiNardo told investigators, he and Kratz returned to the same property, where DiNardo used the backhoe to dig a deep hole and bury the metal tank containing the three bodies.

Kratz gave a similar statement to detectives on Thursday night but claimed that it was DiNardo who shot Finocchiaro, not him, according to court documents.

DiNardo was initially arrested Monday on charges relating to illegal possession of a shotgun and ammunition. He was named a person of interest in the case of the missing men Tuesday but was released from custody after he posted a $1 million bail, 10 percent of which was paid in cash.

But authorities arrested DiNardo Wednesday on charges he tried to sell Meo's 1996 Nissan Maxima a day after the man was last seen. DiNardo's bail was set at $5 million in cash, the highest the judge said she has ever set.

One of his defense attorneys, Paul Lang, told reporters Thursday that DiNardo confessed to killing the four men and told authorities the location of the bodies.

The motive for the killings will come out in time, he added.

DiNardo felt "deep remorse" and was "very emotional," Lang told ABC News.

In the wake of the two arrests, family and friends of the four victims are reeling with the loss of their loved ones.

Patrick's family and friends issued this statement to ABC News on Friday: "We would like to thank everyone for your continued prayers and loving thoughts for both our family and for the other three families during this time of grief. Jimi was an amazing and genuine soul that left us too soon. He was the type of person capable of making anyone laugh whether it be from his sarcastic jokes or his contagious laugh. Aside from his humor, Jimi was incredibly loving and sweet when it came to those closest to him as well as anyone he crossed paths with. We plan to hold all the dear moments we have with him close to our hearts while we seek justice for his untimely passing."

Loyola University Maryland also issued a statement Friday after receiving word of Patrick's death, saying he was a student there and was expected to graduate in 2020. The university said it will plan a memorial Mass for Patrick to be held this fall when students return to campus.

"We have now received the official announcement of the death of Jimi Patrick, Class of 2020. You are probably reeling, as am I, with the news of the loss of a valued member of our community, particularly through such horrific violence," the university's president, Rev. Brian Linnane, said in the statement. "As a community, we are understandably sad, angry, and confused. We will grieve, support one another, and continue to surround Jimi’s loved ones in comfort and prayer. We will also find ways to celebrate Jimi’s life and memory."

ABC News' David Caplan, Michael Claiborne, Gregory Croft, Michael Del Moro, Eva Pilgrim and Stephanie Wash contributed to this report.