When he had finished with the killings, 20-year-old Richard Henderson Jr. took a shower, crawled into his parents' bed and spent Thanksgiving night staring at the ceiling, he told investigators.
The bodies of his mother, father, brother and grandmother, each bludgeoned to death by a metal pipe, lay scattered throughout the small house on the quiet dirt road.
That evening, Henderson scribbled a note and signed his initials:
I knew I did it but I don't know why . . . I didn't kill them out of hate but out of selfishness because I didn't want to die alone.
Henderson later told deputies he methodically killed his family members - one by one, room by room - because they "wouldn't let him leave." He said he wasn't angry at them, but that after he killed his brother, he had to kill the others.
He said he planned to buy enough drugs or poison to kill himself, sheriff's reports stated.
In his two decades, Henderson had proven himself capable of violence, from bringing a gun to school to beating his young wife and threatening to harm their daughter. But his statements provided no clearcut motive for the killings.
Manatee County Sheriff Charlie Wells on Monday said a 6-foot-1, 180-pound Henderson had a troubled relationship with his parents, who had tried in vain to get him help for a drug addiction.
"There was family tension for a long time," Wells said.
Henderson's taped confession provided a chilling account of what happened that night.
He told detectives he sneaked up on his family members, one after another, and beat them to death with a steel pipe more than 2 feet long and 1 1/2 inches in diameter.
He said he killed his 11-year-old brother, Jake, in a bedroom as they played video games. Then he went to his grandmother's bedroom, where 82-year-old June Henderson was reading, and asked her to fetch something from a drawer. When she bent down, he killed her.
He lured his father, 48-year-old Richard Henderson Sr., into the living room to play video games and killed him there. And he beat his 42-year-old mother, Jeaneane, as she sat playing poker on a bedroom computer.
The next day, according to reports, Henderson checked into the GuestHouse International Inn near Interstate 75 in Ellenton, accompanied by his current girlfriend, Danielle Kelvin. He told her his family was in Missouri for Thanksgiving.
They checked out Sunday, and Henderson returned to the family home, where he encountered relatives who had grown worried because they had not heard from the Hendersons in a couple of days, sheriff's officials said.
Henderson told them not to go into the house because his parents were fighting. But one relative kicked in the door, saw a body on the floor in the hallway and called 911.
Later Sunday, Henderson abandoned a Chevrolet van in nearby Wauchula, according to sheriff's reports.
Deputies arrested him as he walked along U.S. 301, not far from Ellenton. He was wearing dark clothes and a backpack and was carrying a smoking pipe in his left pocket that had traces of marijuana on it.
At first, he told deputies his name was Jason, reports show. Then he told them his real name.
Numerous sheriff's and county court records reveal a long pattern of violence and abuse.
In 2001, he was part of a Columbine-style murder-suicide plan that was to have taken place at a local high school but was foiled by police, officials said.
Henderson, then 15, was arrested for bringing a gun onto school property.
He received five years' probation and was ordered to undergo psychiatric treatment.
Records show that only months earlier, Henderson had fathered a daughter, Taylor, with a 14-year-old girl named Brittany Wilde. The couple married in Hardee County in July 2004 - he was 19, she was 17 - but it was hardly a happy union.
Before the year was out, Henderson already had been arrested on charges of domestic battery, aggravated battery and violating a domestic violence injunction that a judge had granted his wife. He also had failed to pay child support for their daughter.
Sheriff's reports say that on different occasions he slapped his teenage bride in the face, kicked her, punched her in the head, shoved her into cupboards and broke her phone when she tried to call for help.
"Then he got a knife (and) walked over and pointed at me and said if I say anything, things wouldn't turn out good," Wilde wrote on one court form. "In the past, Richard has threatened to kill me and our daughter. In May 2002, Richard broke my nose and I left.
"Due to these incidents, I'm in fear of mine and my daughter's safety."
One domestic violence charge was dropped. On another, Henderson pleaded guilty to a lesser charge and was credited with time served.
A judge this year forbade him to see his wife and ordered further psychological evaluation. He also was ordered to complete a batterer's intervention program. Records show he was kicked out of the program in October "due to excessive absences."
Jeffrey Stringer, Henderson's uncle, told WFTS-Ch. 28 that Henderson was the family's "bad apple." Stringer said Henderson's cold-blooded attack and lack of remorse warrants the death penalty.
"Even when he was a kid, he'd grab animals out here and rip their legs off and just laugh about it," Stringer said. "So he was kind of troubled in the first place."
Henderson remained in custody without bail Monday night on four counts of murder.
Back at the modest blue house on 14th Street, near the Hardee County line, investigators continued scouring the crime scene, which Manatee County Detective Bill Waldron described as "extremely gruesome." He said it could take until Wednesday to gather all the evidence.
Across the street, neighbor Annette Segura, 60, continued grappling with the tragedy that had descended on this peaceful slice of rural Florida. She knew the Hendersons well, respected the hard work they put into their lawn care business and cherished their backyard chats.
"I'm still in disbelief," Segura said. "You couldn't ask for better neighbors. You could just go there anytime you needed something.
"I can't believe they're gone."Times staff writer Graham Brink and researcher Cathy Wos contributed to this report, which used information from the Associated Press.