A 17-year-old US boy is accused of bludgeoning his parents to death with a hammer, then hosting a party while their bodies lay in the bedroom.

Tyler Hadley of Florida is charged with twin counts of first-degree murder in the deaths, which authorities say happened on Saturday. He is being held without bond at a juvenile detention centre.

The parents - Blake and Mary-Jo Hadley - were believed to have been struck with the hammer in their heads and torsos sometime after their son posted on Facebook around 1.15pm on Saturday (local time) alerting friends to an evening party at his house, north of West Palm Beach.

Investigators believe the parents were attacked outside their master bedroom and the bodies were 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. When they arrived at 1.30am on Sunday to warn about the noise, the party was already breaking-up, Nichols said.

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

The mother, 47, was an elementary school teacher. The father, 54, worked for a power company.

Autopsies were underway, but police said they believed they died of blunt-force trauma.

Hadley had attended high school, according to police, but had not graduated.

Originally published as US teen 'killed parents, then partied'