SYOSSET, N.Y. (WPIX) – A man who mistakenly thought he was being cut out of his mother’s will shot and killed four family members before turning the gun on himself on the front lawn of his Long Island, New York, home Sunday, authorities said.

“In 41 years, that’s probably one of the most horrific scenes I’ve ever seen,” Nassau County Police Department Commissioner Patrick Ryder said at a briefing Monday.

Joseph Delucia Jr., 59, fatally shot his three siblings and niece while they gathered in the den in the back of the home in Syosset at around noon, according to the police department.

The victims, Joanne Kearns, 69; Frank Delucia, 64; Tina Hammond, 64, and her daughter, Victoria Hammond, 30, were each shot multiple times and died at the scene, officials said.

Delucia fired 12 shots before shooting himself in the chest on the property’s front lawn, police said. The shotgun was recovered at the scene.

“The entire family is now gone,” officials said.

The shooter’s mother died on Aug. 19, and he mistakenly thought he was being cut out of her will, authorities said. Delucia was not cut out of the will but would have had to move from the home he had lived in his whole life, according to police.

“He was panicking. He was being taken care of in the will, but he would have had to move,” an NCPD official said.

Before the incident, neighbors told police Delucia made threatening comments, like “If you hear shots, don’t call the police. It will be too late.”

If Delucia had been reported to have mental health issues, police would have been able to take the otherwise legal weapon from him, officials said.

“As a community, we hear things, and if we don’t say something, sometimes the outcome is like what we saw yesterday,” the NCPD commissioner said.

Neighbors told Nexstar’s WPIX that Delucia was a volunteer firefighter who quit last week in the wake of his mother’s death.