A New Jersey business owner allegedly set fire to his own house in an “elaborate ruse to cover his tracks” of murdering his brother, his sister-in-law, and their two young children before torching their mansion, authorities announced Thursday.

Before allegedly setting fire to his own home in Ocean Township, Paul Caneiro, 52, shot and killed his brother and business partner Kevin Caneiro, 50, outside of his Colts Neck mansion. Then, authorities said, Caneiro allegedly entered the house, stabbed to death his sister-in-law, Jennifer, 45, and their two children, Jesse, 11, and Sophia, 8.

“This one is the most brutal cases that I've seen in my experience here," Monmouth County Prosecutor Christopher J. Gramiccioni said in a press conference on Thursday.

Authorities alleged the murders stemmed from a financial dispute between the two brothers and business partners, who worked together to start a technology firm, Square One, in Asbury Park. On the company’s website, Keith is listed as the founder and chief executive while Paul is named as the firm’s vice president.

Paul Carneiro's “fire was a ruse to make it appear as if the overall Caneiro family was somehow targeted,” Gramiccioni said, adding that police have no reason to believe this case is connected to organized crime and are confident he “acted alone.”

Caneiro has been charged with four counts of murder, one count of aggravated arson, and two weapons charges in connection with the killings and fire in Colts Neck. He was previously charged last week with one count of second-degree aggravated arson for the blaze at this own home.

“My client will assert his innocence and all I will say is all the information is not out there yet,” Robert Honecker, Paul Caneiro’s lawyer, told The Daily Beast.

Authorities allege Carneiro stole evidence from his brother's Colts Neck mansion early Tuesday morning before murdering the family and starting a fire in the basement. Firefighters were not notified of the blaze until 12:38 p.m., when a groundskeeper noticed the smoke.

“The fire in the basement continued to smolder until oxygen caused it to flare as the house was entered,” Gramiccioni said.

Caneiro then returned to his home—a 20-minute drive from Colts Neck—and set it on fire at about 5 a.m., police alleged, to destroy evidence and create the illusion that the entire Caneiro family was being targeted two days before Thanksgiving.

Gramiccioni declined to elaborate as to why investigators believe Paul Caneiro murdered his brother’s family, but announced that an additional financial investigation has been opened.

Along with Square One, Paul and Keith Cameiro had a series of businesses together, including a pest-control firm, EcoStar Pest Management. The pair also previously worked together at Jay-Martin Consulting and shared an address in Staten Island for more than a decade, records show.

"We recovered a great deal of evidence, and that evidence is being analyzed as we speak here today," the prosecutor said.

According to last week’s arrest warrant obtained by The Daily Beast, Caneiro "purposely or knowingly" used gasoline to start a fire at his Ocean Township home while his wife and two daughters were still inside.” All four escaped unharmed and authorities believe he did not intend to hurt his family.

Neighbors previously told The Daily Beast that Caneiro and his wife watched the “horrific” fire from their car while firefighters tried to control the blaze. The family left the home around noon, half an hour before firefighters responded to the fire in Colts Neck.

"The fire was massive and everyone went outside to see it," Dinesh Patel, an Ocean Township neighbor said. "I don’t know what else happened, but I also don't understand why you feel like you need to kill somebody."

At the Colts Neck home, authorities discovered Keith Caneiro, who was Paul’s best man at his wedding, outside with a gunshot wound. Jennifer and the children were found “severely burned” inside the house, Gramiccioni said. Investigators also discovered “several gas cans in the rear of the house.”

Jennifer graduated from the University of Albany and "loved to host family parties for every holiday at her home," her obituary said. Their son, Jesse, was a fifth-grade student at Conover Road School and “excelled in history, especially WWI and WWII," his obituary read. His sister, Sophia, was a third-grader at the same school and was a Girl Scout who loved taking martial-arts classes, her obituary said. She also enjoyed baking with her mom and loved ice skating and the New York Yankees.

“I’d be lying if I stood here and told you this was easy,” Colts Neck Mayor J.P. Bartolomeo said at a candlelight vigil held last week. “We lost four really nice people from our community, who I happened to be friends with, who my boys were friends with.”

Caneiro is scheduled to have his first court appearance on Friday. If convicted, Carneiro faces multiple sentences and Gramiccioni hinted on Thursday he would have pushed for the death penalty if it were an option in New Jersey.

“I would have certified this case as a capital case, but that’s not my job here,” he said.