What we know about the man who confessed to killing 4 in Pa.

The person of interest who confessed Thursday to killing four missing Pennsylvania men has been known to police since he was 14 years old, according to authorities.

Cosmo DiNardo, 20, made the confession in exchange for a promise that the death penalty will not be pursued in his case, according to Paul Lang, one of DiNardo's lawyers.

The most significant offense on the arrest record for DiNardo prior to his confession was a gun charge in February 2017, which was later dismissed and re-filed, court documents show. While none of the crimes detailed in the arrest record were violent, the report does makes a reference to DiNardo suffering from a mental illness.

DiNardo was arrested twice this week before confessing on Thursday, once on Monday on the February charge of illegally possessing a shotgun and ammunition and again on Wednesday on charges of stealing the car that belonged to one of the victims, 21-year-old Tom Meo. He was released Tuesday on $1 million bail, 10 percent of which was paid in cash. A $5 million bail was set Wednesday after DiNardo was taken into custody for a second time.

DiNardo is well known to police

Since 2011, DiNardo has had contact with police more than 30 times, although most of those cases have not resulted in arrests, a law enforcement source told ABC News.

It is unclear what transpired from DiNardo's numerous interactions with police. A request has been placed by ABC News with police for all calls and service to the DiNardo family home in Bensalem Township.

Aside from his arrests this week, DiNardo's most recent interaction with police involved a citation for not having proper boater's education paperwork and other equipment in May 2017.

DiNardo is also well known around town

Residents from Bensalem Township told ABC News that there was something "off" with DiNardo, and that something about him changed after he was injured in an ATV accident that took place roughly seven months ago.

Paul Lang, his attorney, declined to comment on his mental state at a press conference Thursday.

DiNardo is an avid hunter, and would show off the animals he killed, according to residents.

What we know about the victims

Remains of Dean Finocchiaro, 19, of Middletown, were found in a grave 12-feet deep after the search of the vast property owned by DiNardo's family intensified, Bucks County District Attorney Matthew Weintraub said at a press conference early Thursday. He had been missing since Friday.

Finnochiaro was last seen at his Middletown Township home on Friday and was reported missing on Saturday, police said.

Two of the missing men -- Tom Meo, 21, of Plumstead, and Mark Sturgis, 22, were close friends, Sturgis' father told police. Both men were last seen July 7 and failed to show up to work the next day, according to a criminal complaint.

Sturgis' father told police that his son was going to meet up with Meo before he went missing.

The relationships among DiNardo and the remaining victims, Finocchiaro and Jimi Tar Patrick, 19, of Newtown Township, who was last seen on July 5, are unclear.

Lang told the press this afternoon that further details about how the victims died, and where their bodies were located would be released at the discretion of the Distract Attorney's office at a later date.