A family tragedy unfolded in Syosset on Sunday when a distraught son, fearing he would be left out of his recently deceased mother’s will, killed four family members before taking his own life, authorities report.

The murder-suicide occurred just before noon on Wyoming Court, shortly after the death of 95-year-old Theresa DeLucia on August 19. The family was preparing to sell the home, which had been DeLucia’s lifelong residence. Joseph DeLucia Jr., 59, who had a history of mental illness, reportedly believed he would be excluded from the will and left homeless.

In a devastating turn of events, Joseph DeLucia Jr. shot and killed his siblings Joann Kearns, 69, and Frank DeLucia, 64, along with his niece Tina Hammond, 64, and her daughter Victoria, 30, in the rear den of the house.

“The perception of Joseph Jr. was that he was being cut out of the will and would be displaced,” said Detective Captain Stephen Fitzpatrick of the Nassau County Police Department. “Because of that perception and his past mental health issues, he decided to act.”

DeLucia Jr. used a 12-gauge Mossberg shotgun, firing 12 shots that struck all four victims multiple times. After the attack, he reportedly went to the front lawn, where he shouted about what had happened before turning the gun on himself. A neighbor, who overheard his shouts, called 911, leading to the discovery of the tragedy.

“He then fired a self-inflicted shot to the chest,” Fitzpatrick added.

Neighbors described DeLucia Jr. and his mother as long-time residents of the home, with some expressing shock over the incident.

“The mother who owned the house recently passed away. The family was in, and from what I understand, there was possibly a dispute,” said neighbor Corey Margulefsky.