A New Jersey man murdered his brother and brother's entire family before setting their mansion on fire over an apparent financial issue stemming from a joint business venture, prosecutors said Thursday.

Paul Caneiro, 51, was charged with four counts of first-degree murder, one count of aggravated arson, and one count each of possession of a firearm and a knife for an unlawful purpose, Monmouth County Prosecutor Christopher Gramiccioni announced. The charges were in addition to an aggravated arson charge he was served with last week after his Ocean Township home was set on fire.

Gramiccioni said Paul Caneiro murdered his brother Keith Caneiro, 51, his sister-in-law Jennifer Caneiro, 45, and their young children. The murder motives were “financial in nature” and stemmed from their tech and pest-control business, Square One, located in Asbury Park. The prosecutor said an investigation into Paul Caneiro’s finances was launched. He said the investigation was still ongoing.

Paul Caneiro was charged with four counts of murder in the deaths of his brother and his family. (Ocean Township Police Department)

Paul Caneiro repeatedly shot his brother Keith outside his home in Colts Neck in the early morning hours last Tuesday, Gramiccioni said. Caneiro then shot and stabbed to death his sister-in-law and stabbed the children, who were 8 and 11 years old, according to Garmiccioni. He allegedly then set a fire in the basement of the house.

Caneiro then went back to his home in Ocean Township and set fire to his own house with his own family still inside, officials said. The house fire started on the exterior of the house.

Gramiccioni said Caneiro returned to his Ocean Township home with evidence from the Colts Neck crime scene and started the fire at his own home at around 5 a.m. “for the purpose of both destroying evidence of his earlier crimes in Colts Neck and to also create the illusion that the overall Caneiro family was somehow victimized or targeted. We allege that it was a ruse.”

Keith Caneiro and Jennifer Caneiro, who were found dead at their New Jersey mansion after officials responded to a fire at the home last week. (Facebook)

It wasn’t clear what time Paul Caneiro allegedly entered the Colts Neck property. The fire at the mansion was first reported at around 12:30 p.m.

Colts Neck is an upscale community about 50 miles south of New York City and is home to horse farms. Bruce Springsteen reportedly owns a home in the town, and his youngest son, Sam, joined the Colts Neck Fire Department in 2014, NJ.com reported.

Caneiro will make an appearance at Monmouth County Superior Court on Friday.

Fox News’ Travis Fedschun and the Associated Press contributed to this report.