On Wednesday, someone bound and threatened 4 people – a husband and wife, their 10-year-old son, and housekeeper – killed them, then torched their million-dollar home in Washington D.C. On Thursday, all were found dead, and now police are trying to unravel what happened.

The details of the murders and the arson that followed are disturbing.

Police now believe that more than one person is involved, they knew the 4 people found dead and had probably studied their everyday lives. There’s no evidence the perpetrators broke into the million-dollar home, even though it had an extensive security system, according to NBC Washington.

The dead are Savvas Savopoulos, 46; his wife, Amy Savopoulos, 47; their son, Philip, and housekeeper Veralicia Figueroa, 57. Whoever killed them likely entered the house on Wednesday and tied up everyone, perhaps in an attempt to get something from Savvas.

Crews, who arrived at the million-dollar residence on Thursday afternoon to find flames coming from the roof, doused out the blaze and located the 4 dead inside. At least three of them had suffered blunt force trauma or stab wounds, Q13Fox added. One of the victims was transported to the hospital with a head wound; he or she smelled of gasoline.

CEO Savvas Savopoulos; president of American Iron Works, found dead in a burning D.C. home. http://t.co/MT5D8yq9hp — FAM Intl Security (@FAMSECURITY) May 18, 2015

MORE: 2 of the NW house fire victims have been identified as Savvas Savopoulos and his wife Amy Savopoulos. http://t.co/q26vYSDca2 — 99.1 WNEW (@WNEW) May 15, 2015

#dailymail Savopoulos family in DC may have known attackers in murder-arson: Savvas and Amy Savopoulos were fo... http://t.co/TBBjKU0QRs — THAILAND (@nakhon224) May 19, 2015

All four are considered homicide victims and their fatal injuries were inflicted before the fire, the Associated Press reported. Investigators found evidence of arson.

Officials are also trying to determine the significance of a text received Thursday afternoon by a friend of Figueroa. A woman named Nelly often worked with her at the house and was scheduled to be there that day, WTOP added. But someone texted her three hours before the fire, warning her not to come.

According to Fox, that someone was Amy, who said “I am making sure you do not come today.” And the day before that, Savvas called and left her a voicemail, imploring her not to come to work because his wife was sick.

“Sometimes you never understand why something happens, but I’m lucky I’m still here,” Nelly said.

Investigators have a person of interest in the case, who was filmed at a banquet hall near the scene of a car fire; the car was a blue 2008 Porsche. It was stolen from the home and found in a church parking lot.

There are no theories as to why these 4 people were murdered, but the father owns American Iron Works, their house is valued at $4.5 million, and they are known to have had a very valuable art collection. They have two older daughters who were away at boarding school when their parents and brother were killed; they are safe.

Meanwhile, the upscale neighborhood – which has Vice-President Joe Biden as a resident – is shaken up, said neighbor Lisa Lambert.

“Everyone in the neighborhood is incredibly unsettled about this. They were well-liked. It’s surprising to everyone.”

[Photo Courtesy FAM Intl Security Twitter]