A New Jersey technology executive was charged Thursday with killing his brother and the brother's family over a business dispute, and then setting fire to their mansion and his own house in an attempt to cover up the crimes.

Paul Caneiro, 51, was charged with four counts of murder, as well as arson and two weapons violations, in the death of his 50-year-old brother, Keith, along with Keith's wife, Jennifer, and their two children, at their Colts Neck estate, about 50 miles south of New York City. They were shot, stabbed or both.

"This one is the most brutal case I've seen in my experience here," said Monmouth County prosecutor Christopher Gramiccioni.

Caneiro's motive "was financial in nature," stemming from two businesses — a computer systems company called Square One and a pest control business — that he and his brother jointly ran in Asbury Park, the prosecutor said. He declined to elaborate.

Keith Caneiro had some upcoming job interviews planned after getting his master's degree this year, according to Brian Bott, who owns a fitness studio where he worked out. Bott did not know whether he planned to keep working with his brother if he got a new job.

Keith Caneiro, he said, was "a super busy guy," but if he ever mentioned any work stress, it was "nothing relative to something like this."

Paul Caneiro was already under arrest on a charge he set fire to his own home 10 miles away in Ocean Township while his wife and two daughters were inside. The second fire was a ruse intended to make it appear the extended family was a target, the prosecutor said.

There was no evidence he intended to kill his own family, he said. They escaped without injury.

Caneiro's attorneys, Robert Honecker and Mitchell Ansell, said their client loved his brother's family, had no reason to harm them and had been "wrongly accused."

"There is absolutely no reason in the world for Paul Caneiro to have committed the crimes," the statement said, while adding, "Paul Caneiro just couldn't say no to his family."

A criminal complaint said both a gun and a knife were seized from Caneiro, who is scheduled for a court appearance Friday morning.

Keith Caneiro was shot numerous times on the lawn of his mansion in Colts Neck, an affluent horse country town that is home to rock star Bruce Springsteen, and where former "Daily Show" host Jon Stewart and his wife operate an animal sanctuary.

Jennifer Caneiro was shot and stabbed, and the two children, 11-year-old Jesse and 8-year-old Sophia, were stabbed repeatedly, the prosecutor said, disclosing for the first time how the three died.

According to the prosecutor, Paul Caneiro shot his brother on the lawn of the mansion, went inside and killed the rest of the family, and then set a fire in the basement early Nov. 20. He then returned to his own home and set gasoline ablaze outside both ends of the building.

The prosecutor said the fire at Paul Caneiro's house was set to destroy evidence he had brought there from the crime scene, but also had another purpose.

"That fire was a ruse to make it appear as if the overall Caneiro family was somehow targeted," Gramiccioni said.

Investigators found no evidence of anyone else being involved in the crime, he said.

The fire in Paul Caneiro's home was reported at 5 a.m. But prosecutors allege the Colts Neck fire was set before that, even though the mansion blaze was not reported until about 12:30 p.m. The prosecutor said the mansion fire smoldered in the basement for hours before being discovered.

Keith Caneiro had become a morning fixture at Aspire Fitness for the past four years, known for joking with other clients and talking about pizza, veal and other favorite foods. A video Bott posted online shows him doing push-ups with his young daughter Sophia on his back.

Paul Caneiro's wife and adult daughters are also members, but Paul Caneiro, who was in a serious car accident a few years ago, was not. Bott believed he's had some mobility issues since the crash.

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Associated Press writers Maryclaire Dale and Claudia Lauer in Philadelphia contributed to this report. Follow Wayne Parry at http://twitter.com/WayneParryAC

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Information from: NJ.com, http://www.nj.com