Police say Tyler Hadley has been charged with two counts of first degree murder.
Investigators say they found the deceased bodies of Blake and Mary-Joe Hadley in their locked bedroom Sunday morning.
They had been partially covered with household items such as towels, books and pictures.
They say they found a 22-inch hammer in between their bodies and it is believed to be the murder weapon.
The Hadleys suffered blunt force trauma to the head and torso.
"The crime scene was, certainly, a merciless killing," said Port St. Lucie Police Captain Don Kryak.
Jim Wallace lives next door.
"I wasn't quite sure until I saw the (medical examiner) show up, then I knew what was going on," he said Sunday.
Neighbors said the Hadley's 17 year old son had hosted a party with dozens of other teenagers Saturday evening into the early hours of Sunday.
Police say the parents were killed before the party.
They don't think those attending the party knew the bodies were inside at the time.
However, they would like any guests to contact them.
The party began between 9 and 10 p.m.
Investigators allege that after Tyler killed his parents he went on Facebook and invited people to his house for the party.
One of those teenage guests was Mike Young who said he does not know the Hadley's son very well.
"There was a good 50 people that were here Saturday night," said Young.
A neighbor called police because of party noise, but it was not until later Sunday morning when police went into the Hadley home and made the grim discovery.
When police arrived around 4:20 a.m. Sunday for a 'welfare check,' following a tip that a crime had been committed, they say Tyler Hadley appeared nervous and skittish.
They said he said very little.
The couple lived in their residence on Granduer Avenue for at least the past ten years.
"I've known Mary-Joe since she was in high school in Fort Lauderdale. They are a nice family. The kids are always nice. They used to come to our house trick-or-treating and they always called me Miss Charlie," said Charlene Moses, a family friend.
Police say the Hadleys had an older son who did not live at the home.
Tyler Hadley is in custody and being held without bond.
He is in the juvenile system but will be charged as an adult.
Police believe he acted alone and do not expect to charge anyone else in the case.
Police have not identified a motive.
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