One of those men is 20-year-old Cosmo DiNardo. His lawyer previously said his client has confessed his involvement to police.
The other man is 20-year-old Sean Kratz of Northeast Philadelphia. He was taken into custody around 2:30 a.m. Friday.
DiNardo is charged with a number of offenses including four counts each of criminal homicide, conspiracy to commit criminal homicide and abuse of a corpse. He also faces three counts of robbery.
"I'm sorry," a shackled DiNardo said to reporters as he was led away by police on Thursday.
VIDEO: DiNardo leaves building after meeting with DA on Thursday
Kratz is also facing a list of charges including three counts each of criminal homicide, conspiracy to commit criminal homicide, abuse of a corpse, and robbery.
DiNardo is accused of killing Jimi Taro Patrick, 19, of Newtown Township, on July 5, and burying him in a single grave on his parents' land.
DiNardo and Kratz are both charged with the July 7 slayings of Dean Finocchiaro, 19, of Middletown Township; Thomas Meo, 21, of Plumstead Township; and Mark Sturgis, 22, of Pennsburg, Montgomery County. Their bodies were found Wednesday in a 12-foot-deep common grave elsewhere on the same property.
VIDEO: Uncle of Bucks Co. murder victim reacts to arrest
All four men had been shot, according to a probable cause affidavit, which said the suspects both gave statements to police on Thursday.
Each victim has been positively identified, Weintraub said, and their family members were briefed on details of the case on Friday morning.
The only motive disclosed by investigators was that DiNardo said he wanted to set the victims up when they came to the farm to buy marijuana.
READ: Criminal complaint against Cosmo DiNardo
READ: Criminal complaint against Sean Kratz
According to the probable cause affidavit, DiNardo told investigators that he had agreed to sell Patrick four pounds of marijuana for $8,000.
Dinardo said he picked up Patrick at Patrick's home in Newtown on July 5 and drove him to the DiNardo property in the 6000 block of Lower York Road in Solebury, the affidavit says.
RELATED: What we know about Cosmo DiNardo
When they arrived, DiNardo said, Patrick had only $800, so DiNardo offered to sell him a shotgun for that amount, the affidavit says. They walked to a remote part of the property, where DiNardo said he fatally shot Patrick with a .22 caliber rifle, according to the affidavit.
DiNardo then drove a backhoe that was on the property to where Patrick lay, dug a hole no more than six feet deep and buried him, the affidavit states. Based on DiNardo's statement, investigators located Patrick's body in that grave late Thursday.
On July 7, DiNardo told investigators, he agreed to sell a quarter-pound of marijuana to Finocchiaro for about $700, the affidavit states.
VIDEO: DA announces charges against DiNardo and Kratz
DiNardo first picked up Kratz, whom he described as his cousin, and drove to Finocchiaro's home in Middletown. DiNardo and Kratz allegedly agreed on the way that they would rob him, the affidavit says.
DiNardo said he gave Kratz a .357 handgun belonging to his mother, and then drove all three to the Solebury property.
According to the affidavit, he said Kratz shot Finocchiaro in the head as they were leaving a barn on the site.
(NOTE: Kratz gave a similar statement to detectives on Thursday night, the affidavit says, but said that it was DiNardo who shot Finocchiaro, not him.)
DiNardo told investigators he then took the gun and shot Finocchiaro a second time as the victim lay on the ground.
Also on July 7, DiNardo said he met Meo and Sturgis at a church parking lot in Peddlers Village, a short distance west of the DiNardo property on Route 202 in Lahaska, the court records say.
DiNardo told investigators that he had a marijuana "deal" set up with Meo, according to the affidavit.
Meo and Sturgis followed DiNardo to the Solebury property in Meo's Nissan Maxima, Dinardo allegedly told investigators.
VIDEO: Community reacts to news of missing men murders
After parking the Nissan in the 2000 block of Aquetong Road, Meo and Sturgis rode with DiNardo in his truck to the adjacent Lower York Road property, where Kratz awaited, the affidavit states.
After the men exited the truck, DiNardo said, he shot Meo in the back with the .357 handgun, then fired several times at Sturgis as he fled, and Sturgis fell to the ground, the affidavit states.
DiNardo said he then ran over Meo with the backhoe before using it to lift both bodies into a metal tank where he already had placed Finocchiaro's corpse, the court records say.
VIDEO: Chopper 6 over the investigation site Thursday
The following day, DiNardo told police, he and Kratz returned to the property, where DiNardo used the backhoe to dig a deep hole and bury the tank containing the three bodies, the affidavit says.
He allegedly poured gasoline into the metal tank and lit it on fire in an effort to hide their identities, but the DA said that effort was "not successful."
"I don't know what convinced him (to confess). I'd like to think he wanted to get these boys home," Weintraub said at a news conference, explaining the surprise plea agreement forged Thursday that led them to the final body.
Authorities might never have found the fourth body unless they worked with DiNardo, Weintraub said.
"We'd still be looking for Jimi Patrick had we not made this agreement," Weintraub said. "It was so far away (from the others on the farm) that I started to get sick to my stomach on the ride."
DiNardo and Kratz were arraigned on Friday afternoon. The judge denied bail for both men.
They will be jailed separately after prosecutors argued the men were dangers to society.
VIDEO: Homes in NE Philly, Ambler searched in Bucks Co. killings case
The Action Cam was at Kratz's home in the 800 block of Magee Ave. in Northeast Philadelphia's Lawndale neighborhood on Friday after he was taken into custody.
Also Friday, police were searching a home and property in the 400 block of Susquehanna Road in Ambler, Montgomery County. The property is believed to be the home of a relative.
Authorities had charged DiNardo earlier this year with having a gun despite an involuntary mental health commitment. He was arrested on that charge Monday and held on 10% of $1 million bail. He then posted bail on Tuesday.
VIDEO: Cosmo DiNardo arrives at Bucks Co. prison
On Wednesday, he was charged with stealing Meo's car and held on $5 million cash bail. In seeking that bail, prosecutors said he had been diagnosed with schizophrenia. He also suffered a head injury in an ATV accident about a year ago.
DiNardo's parents declined to comment after leaving a government building where he spent several hours with Bucks County District Attorney Matthew Weintraub and other investigators on Thursday.
Kratz told a judge Friday that he had no lawyer. She replied that he should hire one or apply for a public defender.
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