Earlier reports identified the suspect as Daron Dylon Wint, but newly obtained court documents show that this was just one of several aliases that he apparently used; his legal name is Darron Dellon Dennis Wint.
Prosecutors alleged that Wint did not pull off the slayings and arson on his own.
The crime "required the presence and assistance of more than one person," according to the criminal complaint.
Court documents reveal that the incident began sometime after 6 p.m. on May 13, and continued through the afternoon of the next day. The fire at the mansion was reported at 1:24 p.m. on May 14, but the victims had been held against their will since the previous day.
Wint's attorney questioned the evidence, but the judge went forward with the charges and ordered Wint to remain imprisoned without bond.
As of Friday, no one else had been charged in connection to the killings.
D.C. Police Chief Cathy Lanier said, "it's pretty obvious that there was coordination" in the crime, but cautioned that it remains unclear what form that help took.
Lanier told CNN: "Whether there was someone else that actually took part in the kidnapping and the murder, it's going to take time to get this evidence together, and we just don't want to jump to conclusions or draw conclusions too soon."
While five others who were arrested along with Wint had been questioned and released, investigators are interviewing others, the chief said.
A grisly discovery
The arrest came a week after the grisly discovery of the bodies of Savvas and Amy Savopoulos
, and their son, Philip.
The fourth victim, housekeeper Veralicia Figueroa
, was found alive at the home and taken to the hospital, where she died.
A day after they "barely missed" catching him in New York, Cmdr. Robert Fernandez of the U.S. Marshals Service said, authorities spotted Wint, 34, leaving a Howard Johnson hotel in College Park, Maryland.
They tracked, surrounded and stopped Wint, who was riding in the back of a Chevrolet Cruze, and they also stopped a small moving truck that had been traveling alongside in northeast Washington.
Officers found $10,000 in cash during the arrest, according to the criminal complaint
Three women were with Wint in the car, and two men were in the moving truck, including Wint's brother.
Though questions remain, the victims' families breathed a little easier knowing that a suspect is in custody.
"While it does not abate our pain, we hope that it begins to restore a sense of calm and security to our neighborhood and to our city," the Savopoulos family said in a statement.
Signs of trouble before the fire
in the $4.5 million home in one of Washington's toniest neighborhoods, not far from the home of Vice President Joe Biden, was a story in itself.
But soon it became evident that the blaze wasn't the full story.
The victims were bound with duct tape, and they suffered from blunt-force trauma, according to a source familiar with the investigation. There were signs that Philip, the 10-year-old son, had been stabbed and tortured, according to the source.
According to court documents released Friday, the boy's body was found in a bedroom on the second floor, which sustained heavy fire damage. The body was on the charred remains of a queen-sized bed, the documents state. The fire consumed a majority of the bed frame.
Figueroa's husband, Bernardo Alfaro, raised the prospect that the victims' torment started a day earlier, telling CNN affiliate WJLA-TV that his wife didn't come home the night of May 13.
Alfaro knocked on the mansion's door the next morning, noting that family's blue Porsche was parked on the street. He knew something was wrong, according to WJLA. He suddenly got a phone call from Savopoulos telling him that Figueroa was at a hospital with Amy Savopoulos, who wasn't feeling well.
"I started thinking, 'Why? She doesn't drive. She doesn't speak very good English,' " Alfaro said.
A second housekeeper, Nelitza Gutierrez, also received a text message from Amy Savopoulos hours before the fire began, telling her to stay home. It came a day after Gutierrez got a voice mail message from Savvas Savopoulos telling her not to come the following day because his wife was sick.
"Sometimes you never understand why something happens, but I'm lucky I'm still here," Gutierrez told CNN's Joe Johns.
Source: 'Whoever was in the house was looking for money'
What really happened is largely a mystery. The motive for the killings has not been divulged, but investigators are considering that money may have been a prime factor.
"Whoever was in the house was looking for money," said the source familiar with the investigation.
According to the court documents, as the episode unfolded inside, one of Savopoulos' employees came to the home and dropped off $40,000.
Wint and other suspects made off with the money, the documents state.
The money had been earmarked for a martial arts studio that Savvas Savopoulos was opening up in Chantilly, Virginia. Savopoulos was a martial arts enthusiast, according to online posts, and Wint once worked for American Iron Works.
Savvas Savopoulos was the CEO and president of American Iron Works, a building materials manufacturer based in Hyattsville, Maryland.
DNA on pizza crust
Investigators identified Wint as a suspect in an unusual way.
On the night of May 13, a Domino's deliveryman brought two pizzas to the Washington home while the family members and their housekeeper were being held inside against their will, according to the criminal complaint.
The pizza boxes were found in the same place where three of the victims were located.
The pizza was ordered by a woman -- believed to be Amy Savopoulos -- and paid for with her credit card, according to the court documents.
The pizza order included instructions for the pizza to be left at the door because the woman who ordered it claimed she was nursing a sick child and couldn't come to the door, the documents state.
The delivery man placed the pizzas on the front porch, rang the door bell, and left.
Investigators said they traced Wint to the scene after finding his DNA on pizza crust.
Ex-lawyer calls Wint 'kind, gentle, nonaggressive'
An attorney who represented Wint in six earlier cases -- none of which, he says, ended in guilty verdicts -- said he believes authorities have "the wrong guy."
Even if his DNA was found on pizza crust, it doesn't mean Wint went inside the Savopoulos mansion, much less bound and killed anyone, attorney Robin Ficker told CNN's "New Day."
A video released by Washington police of a man outside the mansion didn't show any identifying facial features, the attorney said.
"I know him to be a kind, gentle, nonaggressive person; (he is) someone you wouldn't mind your grandmother going to lunch with," the Maryland lawyer said. "... It's a rush to judgment. There's a presumption of innocence, which is not being mentioned by police."
According to court records, Wint has faced multiple charges over the years, including theft, assault and a sexual offense. He was cleared of some of them, but he has three assault convictions in New York.
He attended Marine Corps recruit training in 2001 but left before completing the camp. It was not clear why.
A neighbor of Wint's parents expressed sympathy for them.
"I feel very sad for them, for the pain they're going through, which is not their fault," Devera Zianal said. "Whatever happened, if he is guilty, he had choices. I know he was not raised this way."