The will of the deceased woman who resided in the home that led her son to commit a massacre of his siblings.

This narrative explores the topic of suicide. In case you or someone you know is experiencing suicidal thoughts, kindly contact the Suicide & Crisis Lifeline at 988 or 1-800-273-TALK (8255).

More than a decade ago, Theresa DeLucia, a 95-year-old mother of four from New York's Long Island, had already expressed her wishes in a last will and testament before her passing last month.

In 2007, the document may have contributed to her youngest son's shooting spree, which resulted in the deaths of his three siblings and a niece in a murder-suicide.

Joseph DeLucia received one-fourth of the value of the home's sale and a quarter of the rest of his mother's estate, with Zillow estimating the property value at almost $900,000.

DeLucia resided with his mother until her passing, but in her will, she instructed any family members living in the same home at the time of her death to vacate it in order to facilitate its sale.

She also empowered her oldest son, Frank, to enforce the provision.

Joseph killed the rest of his family out of fear of being homeless.

Read Theresa DeLucia's last will and testament

Nassau County Police Commissioner Patrick Ryder described the scene as one of the most horrific he's ever seen after 41 years.

If the warning signs had been reported to police, the slayings could have been prevented, according to him.

"In that community, there was discussion about the grief of the shooter who refused to leave his home after his mother passed away," he stated. "In the past, there was community chatter that if you hear gunfire, don't call the police – it'll be too late."

On the morning of Aug. 25, family members met at the DeLucia matriarch's home on Wyoming Court in Syosset to discuss selling the home with a real estate agent. The suburban neighborhood is located about 30 miles east of New York City.

Just before noon, a neighbor called 911 and discovered Joseph DeLucia, 59, lifeless outside, with a shotgun nearby on the grass.

Joanne Kearns, Frank DeLucia, Tina Hammond, and her daughter Victoria were discovered inside the house.

According to authorities, Joseph DeLucia had a history of mental illness but no significant criminal record beyond a drunken driving stop decades ago. However, under New York's red flag law, police could have seized his shotgun, police said.

Stephen Fitzpatrick, Nassau Detective Capt., stated that the murderer felt he was being excluded from the will and would have been homeless if his siblings sold the house.

He decided to get a loaded Mossberg shotgun, 12-gauge, and approach them in the rear area of the house, firing 12 shots from the kitchen, striking all four of them multiple times, because of that perception, he told reporters at the briefing.

Before DeLucia fired a final shot into his own chest, neighbors heard him shouting on the front lawn. A haunting final post on a Facebook page under his name shows a New York license plate reading, "DEPRSSED."

Fitzpatrick advised that if anyone believes someone else has problems, they should contact us.

Mary Macaluso, a local realtor, informed Newsday that she was scheduled to meet the family but arrived to find the block barricaded with police tape.

This narrative explores the topic of suicide. In case you or someone you know is experiencing suicidal thoughts, kindly contact the Suicide & Crisis Lifeline at 988 or 1-800-273-TALK (8255).