Troy Victorino, 27, Robert Cannon, 18, Jerone Hunter, 18 and Michael Salas, 18, are charged with first-degree murder and armed burglary. The teens confessed shortly after they were arrested Saturday, authorities said.
At a hearing Monday attended by some relatives of the victims, all four men were denied bond and had public defenders appointed for them.
"I wanted to see this. I wanted to see who murdered my daughter," said Kay Shukwit, mother of 19-year-old Michelle Nathan. "I want to look at him."
Police said the attack was the brutal culmination of an argument between Victorino, an ex-convict, and one of the victims, who is believed to be Erin Belanger, 22. She was singled out for a beating so vicious that even dental records were useless in trying to identify her.
Four Florida probation officers were fired Monday for allegedly failing to keep custody of Victorino.
Corrections Secretary James Crosby said the probation officers missed two key opportunities to put Victorino in jail, including one on the same day as the killings.
Crosby said Monday he had no answer for why Victorino slipped through the cracks.
"There is no excuse for this inaction," Crosby said.
Belanger's grandparents, from Maine, own a winter home in Deltona, between Orlando and Daytona Beach, which was supposed to be vacant this summer, but police said Victorino and other squatters used it in July as a party spot.
Joe Abshire, Belanger's brother-in-law, said she had talked to him last Sunday about heading to the vacant house to go swimming one day and finding about six people living there. The squatters were kicked out, but the Xbox video game system and clothes were left behind. Belanger took the items back to the three-bedroom rental home she shared with friends.
Over the next days, deputies were called to the grandparents' house six times. The victims also reported a tire-slashing at their home and a threat.
The squatters warned Belanger that "they were going to come back there and beat her with a baseball bat when she was sleeping," Abshire told The Sun of Lowell, Mass., for Sunday editions.
All four suspects were armed with aluminum bats when Victorino kicked in the locked front door, according to arrest records. The group, who wore black clothes and had scarves on their faces, grabbed knives inside and attacked victims in different rooms of the three-bedroom house, authorities said.
The victims, some of whom were sleeping, did not put up a fight or try to escape, Sheriff Ben Johnson said. All had been stabbed, but autopsies determined the cause of death was the beating injuries. Victorino, the last to leave the house, took the Xbox, police said.
Left behind were the bodies of Belanger and Nathan; as well as Anthony Vega, 34; Roberto "Tito" Gonzalez, 28, who recently moved from New York; Belanger's boyfriend, Francisco Ayo Roman, 30; and Jonathan Gleason, 18. They lay in bloody beds, on bloody floors. There were crimson spatters on the walls and the ceiling.
"Another senseless killing, multiple killing. I mean, it's over clothes and an Xbox. And a vendetta," Sheriff Ben Johnson told CBS affiliate WKMG-TV. "They walked into this house with the intent of killing the people in the house. And you had six innocent victims in this residence."
Johnson, a 33-year veteran of law enforcement, called it "the worst thing that I've ever seen in my career. The brutal force used against the victims ... it's indescribable."
Victorino has spent eight of the last 11 years in prison and was arrested Saturday for a probation violation. His first arrest was in an auto theft when he was 15, according to state records. He has prior convictions for battery, arson, burglary, auto theft and theft.
Hunter, who was with Victorino when he was arrested Saturday, agreed to accompany investigators for questioning. Police said he admitted his role in the slayings and identified the other two suspects.
"He was a good kid, he just got with the wrong crowd," said Hunter's father, Dan Washington. "He never seemed to be that type ... that was violent."