A mass suicide on a quiet cul-de-sac in Nassau County left five people dead Sunday, days after the family matriarch died and relatives tried to sell the house, police and sources said.

All of the victims were shot inside the small blue house on Wyoming Court in Syosset, while the gunman killed himself on the front lawn, Newsday reported.

“The mother had just died and they were in the process of selling the house,” said Mary Macaluso, a local real estate agent. She pointed out that she was supposed to meet the relatives at the house around noon – but when she arrived, the road was already blocked off by authorities.

“The kids were all here for the funeral and they asked me to come over and look at the house,” Macaluso told the outlet.

She said one of the children asked her to meet with the family so they would know what to do before putting the house up for sale, which was valued at nearly $900,000 on Zillow.

They also wanted to get it done quickly because two family members had traveled from Florida for the funeral and would be returning soon, she said.

The homeowner, identified in public records as Theresa Martha DeLucia, died early last week at the age of 95, according to her obituary.

“This appears to be a murder-suicide,” Nassau County Police Chief Patrick Ryder told Newsday at the scene. “We know the person shot himself on the front lawn.”