Authorities said they are looking at pursuing homicide charges against a 20-year-old man who was taken into custody earlier on Wednesday (Thursday NZT) and whose parents own the farm.
DiNardo was seen exiting the Bucks County Courthouse on Thursday evening saying, "I'm sorry".
Weintraub said there was an attempt to burn the bodies, but investigators do not believe it was successful.
Those gruesome details emerged as DiNardo and his cousin Sean Kratz, 20, of Philadelphia, were charged with multiple counts of conspiracy, homicide and abuse of a corpse as the investigation into their slayings shifted focus to Kratz's role in the case.
DiNardo agreed to plead guilty to four first-degree murder counts, attorney Paul Lang said outside court.
Finochiaro, 22 year old Mark Sturgis, 21 year old Tom Meo, and 19 year old Jimi Tar Patrick vanished last week.
All four men were discovered buried deep underground on the sprawling property owned by Dinardo's parents in Solebury Township, according to a statement from the district attorney's office.
"They are down 12 foot deep in a hole that is getting deeper by the minute", District Attorney Matthew Weintraub said. "They have done nothing to deserve this awful, unspeakable tragedy that has been beset upon them".
DiNardo also had been arrested Monday and held on US$1 million (NZ$1.37 million) bail on an unrelated gun charge before his father paid US$100,000 (NZ$136,500) to bail him out on Tuesday (Wednesday NZT). Sturgis, Meo and Finocchiaro disappeared two days later.
Authorities have confirmed Finocchiaro's body was found.
That same night, DiNardo said, he met Meo and Sturgis together at a parking lot in Peddlers Village. Sturgis was shot as he tried to run away and fell to the ground. DiNardo told investigators he had a "deal" set up with Meo. The men then dropped the bodies into the roaster, added gasoline and set it on fire. Authorities said they've found human remains in their search for four missing young Pennsylvania men and they can now identify one victim. "I'd like to think he wanted to get these boys home", Weintraub said, explaining the surprise plea agreement forged Thursday that led to the final body.
ORIGlNAL STORY: Pennsylvania authorities and the Federal Bureau of Investigation are searching for four young men between the ages of 19 and 22 who vanished within days of each other last week, one on Wednesday and three on Friday.
"He's told me and my friends, 'Yeah, I've killed people before, I just haven't been caught, '" the man said. They drove him to Dinardo's family property at Lower York Road in Bucks County. Later, Dinardo drove the backhoe back to the location where he shot Patrick, and buried his body in a hole about six feet deep.
Weintraub praised the efforts of investigators, who have worked in shifts around the clock since Sunday to locate the bodies.
Despite the mental health commitment and frequent interactions with police, DiNardo still managed to sell guns and marijuana in the area, according to a source familiar with DiNardo's confession who spoke to the AP on condition of anonymity.
Described by one neighbour as "nutty", Cosmo DiNardo is now being held on $5 million bail after being charged with trying to sell one of the victim's cars.
Finocchiaro's other relatives also posted on Facebook, writing about their struggle to cope with the news.
DiNardo's lawyer says his client is remorseful.
FOX 29's Dave Scratwieser reports Kratz has a criminal record, including two drug arrests in Bensalem.
A Pennsylvania man confessed involvement Thursday in the deaths of four missing men in eastern Pennsylvania, his lawyer told reporters Thursday.