Motive revealed in horrifying LI murder-suicide as cops ID killer as former EMT Joseph DeLucia Jr., who slaughtered relatives after mom’s death

A former EMT slaughtered three of his siblings and a niece as they gathered at his deceased mom’s Long Island home to discuss plans for her estate — and the killer was upset that he’d have to leave the house after they sold it, authorities said Monday.

The shooter — 59-year-old Joseph DeLucia, Jr. — had spent his entire life in the Syosset home owned by his 95-year-old mom, Theresa DeLucia, who died early last week, Nassau County Police Capt. Captain Stephen Fitzpatrick said at a press conference.

But if the family sold the Wyoming Court house, he’d need to find somewhere else to live — and DeLucia had nowhere else to go.

In his rage, DeLucia levelled a pump-action Mossberg 12-gauge shotgun at his three siblings — Joanne Kearns, 69, of Tampa, Florida; Frank DeLucia, 64, of Durham, North Carolina; and Tina Hammond, 64, of East Patchogue — and gunned them down in the house’s den, Fitzpatrick said.

He also murdered his niece, 30-year-old Victoria Hammond of East Patchogue, before running out to the front yard and turning the shotgun barrel on himself, Fitzpatrick said.

“Officers found him with a self-inflicted gunshot wound to his chest,” the captain said. “He was pronounced at the scene.”

Joseph DeLucia, auto mechanic and former EMT who killed 4 in LI murder-suicide, was a hoarder: cops

A neighbor called 911 when they heard DeLucia screaming in the yard — just before he killed himself.

“We heard a high-pitched scream, it was Joe screaming, then one shot,” neighbor Sandy Landsman, 73, told The Post. “I was shocked. I never would have thought beforehand that this would happen.

“We heard he was very upset over this,” Landsman added, referencing the proposed house sale. “He didn’t know where to go, he had lived there his whole life. One of the siblings said she would take care of him, that she would let him come and live with her. Apparently, that didn’t sound too good to him.”

Fitzpatrick said investigators have been told that DeLucia had past mental health problems, but cops have not confirmed that.

But neighbors buttressed this, saying the former EMT suffered from mental illness that had been exacerbated by his sorrow over his elderly mother’s Aug. 19 death.

“There were challenges. It’s really sad,” said Wendy Paisner, who lives across the street from the grisly scene. “But his mother passed away and I think that triggered him. You know, that they were selling the house.”

Landsman, the other neighbor, added that DeLucia was known on the tiny cul-de-sac for letting loose blood-curdling screams whenever he got frustrated.

There were indicators of his emotional problems, Landsman said, and precursors to the banshee wail that DeLucia let loose right after the murders.

“He didn’t say anything — just a high-pitched scream,” Landsman said. “I had heard him scream like that before — whenever he gets frustrated or really upset, he lets that out.

“He’d be out working in front of the house on his car, or his mother’s car, and he would be trying to fix something and he’d break something and he’d scream just like that,” the neighbor added. “You never heard anybody else scream like that though.”

Police identify victims in LI family murder-suicide

Fitzpatrick said DeLucia worked as an auto mechanic for a local car dealership — and was “kind of a hoarder.”

“He spent all his money on tools and stuff,” the captain said. “The house was pretty much hoarded, packed with tools, stuff involved with an auto mechanic.

“He was living there his entire life, never lived on his own,” Fitzpatrick continued. “So you could see his mindset, where his world was now changing and he was in a panic.”

Frustrated Facebook posts on DeLucia’s page implied that he wasn’t always thrilled with his customers.

“Here we go again, another guy who puts his spin-on oil filter back with a cap wrench. This is incorrect. It should be hand tight only. No one gets this,” one post said.

“If you do not know what a air hose coupler or coupling is then you should not be working in an auto-repair shop,” said another post, this one in all capital letters. “You should know all of your equipment by name.”

He had also updated his Facebook cover photo to a New York license plate that simply said, “Deprssed.”

But there was money to be made in selling their tiny home with the blue siding.

Although it wasn’t in the best of shape — with a dated exterior, heaving walkways and a sparsely-covered lawn — it would still likely sell for almost $900,000, according to a Zillow estimate.

A local real estate agent, Mary Macaluso, told Newsday that the late matriarch’s kin contacted her to swing by the home Sunday in preparation for selling the property. But when she got there that afternoon, police had already taped off the street.

CLICK HERE TO SIGN UP FOR OUR METRO DAILY NEWSLETTER

“When this happened, they arrived to meet the realtor,” Fitzpatrick said. “They brought Starbucks, they were assembled in the den area — the brother had stayed behind.”

Macaluso didn’t respond to multiple inquiries by The Post.

DeLucia fired 13 shots in total — 12 aimed at the victims, and one for himself, the captain said. This means he had to reload several times.

There had been only one prior call to the house — a 2022 wellness check that didn’t lead to any police action, Fitzpatrick said.

DeLucia was also arrested for drunk driving in 1983. Other than that, his record was clean.

Police sources said there’s no indication of foul play in matriarch Theresa’s death.

An online obituary described Theresa — known affectionately as “Terry” — as a “beloved and cherished member of the Syosset, New York community,” according to Smokin’ Cues.

Born and raised in Syosset — an Oyster Bay hamlet on Long Island’s North Shore — Theresa spent three decades as a nurse in a local hospital and volunteered at local shelters and food banks, the obit read.

“Theresa was known for her gentle nature and ability to comfort her patients with a smile or kind word,” the obit read. “Her colleagues and patients remember her as a kind soul who always went the extra mile to ensure the well-being of those in her care.”

But when this “beacon of light in her community” passed away, it sent her youngest son into a tailspin.

The scene DeLucia allegedly left at his childhood home shocked even the officers who responded.

“In 41 years, that was one of the most horrific scenes I’ve ever seen,” Nassau Police Commissioner Patrick Ryder said.

— Additional reporting by Dorian Geiger, Larry Celona and Isabel Keane

For the latest metro stories, top headlines, breaking news and more, visit nypost.com/metro/