A 17-year-old boy in Florida has been accused of bludgeoning his parents with a hammer, then holding a party with dozens of friends while their bodies lay in the bedroom, according to police.

Tyler Hadley of Port St Lucie is charged with two counts of first-degree murder, which authorities say took place on Saturday. He is being held without bond at a juvenile detention centre.

Blake and Mary-Jo Hadley were believed to have been struck in the head and torso with a hammer sometime after Tyler had posted on Facebook, around 1.15pm on Saturday, inviting friends to an evening party at his house, about 50 miles (80km) north of West Palm Beach.

Investigators believe the parents were attacked outside their master bedroom, and that their bodies were then moved into the bedroom and the door locked.

As many as 60 people attended the party that night, according to Port St Lucie police spokesman Tom Nichols. They were loud enough to prompt a noise complaint and a visit by police officers. When police arrived at 1.30am on Sunday to warn about the noise, the party was already breaking up, Nichols said.

The police then received a tip that murder may have taken place and returned to the home at 4.20am, where they found the bodies covered with towels, files, books and other household items, and the hammer between them.

Mary-Jo Hadley, 47, was an elementary school teacher. Blake Hadley, 54, worked for Florida Power and Light.

Autopsies were under way, but police believe they died of blunt-force trauma. They said the motive behind the killings was unknown.