CARMEL, N.Y. (CBSNewYork) -- Investigators in Putnam County released the results of their probe Thursday into the horrific blaze that left four people dead and determined a smoldering cigarette ash ignited the fire.
Larchmont Police Capt. Thomas Sullivan, his wife Donna, and their daughters -- 17-year-old Megan and 15-year-old Mairead -- were killed in the May 1 blaze that destroyed their house at 19 Wyndham Lane in Carmel.
1010 WINS' Al Jones Hears From Investigators
Grim-faced investigators laid out the awful truth after five weeks of examining the debris of the Sullivan house. They said the fire was an accident caused by the sole survivor, Thomas Sullivan, Jr., who managed to escape the blaze through the garage.
WCBS 880's Peter Haskell With More On The Story
Cigarette ash smoldering in the mulch off the front steps ignited the early morning blaze and Carmel Police Lt. Bryan Karst said the smoker was 20-year-old Sullivan Jr. The ash smoldered for four hours until the wind fanned embers into flame, CBS 2's Lou Young reported.
Investigators said Sullivan Jr. didn't try to hide what happened.
"It was revealed that he had been smoking several times during the evening at the point of origin on the front porch, down by the stair area," Karst said. "Right away he told us, yes, he smoked and it was his practice to in this particular spot."
The mulch was dry and the smoke detectors apparently were not working, 1010 WINS' Al Jones reported. Investigators said the Sullivan house had hard-wired smoke detectors, but the fire moved so fast, there's no way to know if they went off before it was too late.
"It was the perfect storm and it just took off and the fire went unnoticed for quite a while," said Putnam County Fire Investigation Capt. Dan Tompkins.
Thomas Sullivan got his son out of the home and went back in for his wife and two daughters, but all four perished.
Investigators also said the home's construction -- a popular style of pressed board, glue and light-weight truss construction that burns fast -- contributed to how quickly the home was engulfed, despite the fact it was up to code.
Meanwhile, Sullivan Jr., who learned the official cause of the fire late Wednesday night, is staying with an aunt.
"He's taking this very hard and is going through the grieving process," Karst said.
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