Cosmo DiNardo's chilling confession to Bucks County murders

It was the case that gripped the country--four incomprehensible murders in Bucks County. Tonight, we are hearing Cosmo DiNardo's chilling confession.

It's the voice of Cosmo DiNardo. The words of an admitted cold-blooded killer as he confessed last July to the brutal murders of four Bucks County young men on his father's farm in Solebury Township.

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"I shoot Tom in the back. Drop him. Mark's like what the....(noise). He was such a big kid, I unloaded the gun on him," DiNardo says in a 4-hour long videotaped confession.

It's mid-July and DiNardo is describing his murder spree to detectives and prosecutors as they continue to search for the victim's bodies on the massive 90-acre property after DiNardo admittedly lured them to the site for the sale of marijuana. He coldly describes how he slaughtered them.

"So I dropped him, so he's paralyzed. He says I can't feel my legs. I can't feel my legs," DiNardo explains.

Detectives press him for more detail on how many times he shot one of his victims.

"How many times did you shoot mark? I shot at him I think five times," DiNardo tells police.

DiNardo goes on to explain in chilling detail how he finished off one of his victims with a backhoe, which he later used to bury all four young men on the farm.

"I run, grab the machine. I back until I run him over--dead instantly," DiNardo recounts for the detectives in the room.

The 21-year-old killer even described what he told his alleged accomplice Sean Kratz to say to police if they showed up at the farm while he was attempting to hide the victims' bodies.

WATCH: Victim's lawyer weighs in on Cosmo DiNardo's confession tape, guilty plea

"Stand guard here. If anybody comes tell them it's private property, if you don't have a warrant or something get the f.....out of here," DiNardo tells investigators.

Finally, DiNardo admits to investigators how he tried to cover up his crimes by putting the bodies in a 12- foot trench, then pouring gasoline on the bodies and burning them.

"I had gasoline that was used--couple jugs of it. Took a jug or two, doused them and you know Sean had cigarettes. I don't remember who lit it," he said.

While it was discussed in open court, the district attorney says DiNardo's confession has not been entered into evidence at this time. It is expected to be used at the trial of Sean Kratz after he refused Wednesday to plead guilty. He faces first-degree murder charges and a possible death sentence.

DiNardo was taken away to state prison Wednesday where he will serve a life sentence.