Tyler Hadley, the Florida teen who threw a party after allegedly bludgeoning his parents to death on Saturday, confided details of the double murder to a friend.

Police say the 17-year old high school dropout told his best friend, Michael Mandell, that he was possessed by the devil and took three ecstasy pills before killing each of his parents with a 22-inch framing hammer.

Hadley confessed the killings to Mandell, who he has known since both were eight years old, while the party was in full swing.

After he told me I didn't believe him, because he's been my best friend forever I would never suspect anything like this, Mandell told WPTV.

According to the Port St Lucie arrest affidavit, Hadley had earlier warned Mandell that he was planning to kill his parents that day. But as Mandell had heard similar empty threats in the past, he did not take his friend seriously.

Mandell has been identified as the anonymous person who tipped off police in the early hours of Sunday morning.

Police went to Hadley's Port Lucie home for a well-being check, where they found a nervous and panicky Tyler Hadley, along with beer bottles strewn about.

The bodies of Mary Jo Hadley, 47, and Blake Hadley, 54, were quickly discovered in the master bedroom, under a pile of books, files, towels, anything that he could find inside the home to cover the bodies.

Police believe the double murder took place after Hadley had posted a Facebook invitation to the party at about 1:30 pm on Saturday. Somewhere between 40 and 60 guests arrived to the Hadley home beginning at 9 pm, ignorant to the fact that they were entering a crime scene.

Sometime between 9 and 10 pm on Saturday, Hadley asked Mandell to walk outside with him, where he promptly revealed what he had done. When Mandell claimed not to believe him, Hadley pointed to his parents' cars in the driveway, and led Mandell to a bloody shoe print in the garage.

At some point - the affidavit does not indicate exactly when - Mandell opened the door to the Hadley's parents' master bedroom and saw Blake Hadley's legs under a pile of items.

Hadley went into great detail about the brutal killings in his confession to Mandell. He admitted to taking away his parents' cell phone before attacking them so they would not be able to call for help, and described how he stood behind his mother, undetected, for a full five minutes before bringing the hammer down on her.

Tyler said that his mother turned around when he began to bludgeon her, and asked Why? Shortly after, his father entered the room, and after locking eyes with him for a moment, Tyler murdered him in the same manner.

He told Mandell it took three hours to clean up the blood and that it had been more than he had expected.

Tyler also told his friend that he was planning on taking 10 Percocet painkillers in order to kill himself before he could be arrested.

The crime scene was certainly a merciless killing, Port St. Lucie Police Capt. Don Kryak said. It was brutal.

Hadley is a high school dropout and had previously injured a child in an accident while driving a car registered to his father. The family of the injured child was suing the Hadley's for $15,000.

A neighbor told a local news station that he heard Mr. and Mrs. Hadley had refused Tyler's request to host a party, but it is not known whether that is the motive for the killing.

Tyler Hadley was denied bail. Initially, he was to be tried as an adult for two counts of first-degree murder, but the charges have been reduced to two counts of second-degree murder, which means that Hadley will be spared the death penalty.