Carmel fire: Son's cigarette, dry weather, wind were factors in fatal blaze

He’ll never forgive himself.

The sole survivor of a Westchester blaze that killed his entire family — a police-captain father, mother and two sisters — accidentally sparked the inferno last month when he flicked a cigarette on dried-up mulch, officials revealed yesterday.

“The young man was in shock,” Carmel Police Lt. Brian Karst said about Thomas Sullivan Jr., 20.

“For somebody who was in shock, he was very honest and forthright with us.”

Sullivan smoked twice on May 1 — between 8 and 10 p.m. — right next to the front porch of his home in Carmel, Putnam County, fire investigators explained.

Smoldering ash from one of the cigarettes landed on the dried-out mulch and burned for hours — growing when late-night winds began to pick up.

“It lied in an area, burned and rolled for a while and took off,” said Dan Tompkins, captain of the Putnam County Fire Investigation Unit.

He added the fire was “not considered to be suspicious in nature and was not intentionally set.”

Sullivan won’t be charged with a crime, Carmel Police Chief Michael Johnson said.

The fire intensified at about 2 a.m. and engulfed the home on quiet Wyndham Lane in minutes, officials said.

Four months of dry weather and the home’s lightweight construction — vinyl, wood and plastic — accelerated the flames, officials said.

“There’s a fire in the house!” yelled Thomas Sullivan, 48 — a former NYPD cop who worked in The Bronx — when the blaze began consuming the two-story home.

Thomas Jr. was awakened by his father’s screams. He managed to crawl down the stairs and out the garage door as the inferno spread upstairs and filled the house with smoke.

But the yellow colonial collapsed moments later — burying the elder Sullivan, his wife, Donna, 48, a nurse, and high-school students Meaghan, 18, and Mairead, 13.

Four dogs also died in the inferno, including Mairead’s two pets.

The heat was so intense that it melted the siding of two nearby homes and prevented firefighters from going inside.

It took three hours for the units from Carmel and three other Putnam towns to extinguish the inferno, and investigators had to use cadaver-sniffing dogs to find the charred bodies.

Sullivan was treated for smoke inhalation at Danbury Hospital and released hours later.

He was interviewed at the scene and again for two hours several days later.

He’s been living with his grandfather in Dutchess County since the tragedy.