A police captain, his wife and two daughters died from breathing smoke and carbon monoxide as their home was consumed by fire, a coroner said Wednesday.

The Putnam County coroner, William Stahl, said that "probably" means they died before being burned. He said the autopsy finding that asphyxiation caused the deaths was preliminary, pending microscopic examination of tissue and toxicology tests.

Larchmont police Capt. Thomas Sullivan; his wife, Donna; and his daughters, 18-year-old Meaghan and 13-year-old Mairead, died early Tuesday morning at their Carmel home.

Their bodies were "pretty much burned," police Chief Michael Johnson said.

Carmel police said Wednesday that they had determined where the fire started — on the north side of the front of the house — but did not yet know the cause. Police said the investigation could take several weeks.

The Sullivans' 20-year-old son, Thomas Jr., escaped after he heard his father shouting that the house was on fire, Johnson said. An uncle told The Journal News that the son told him his father then ran back inside to try to rescue his wife and daughters.

"Tommy Sullivan was a hero," said the uncle, Thomas Zielinski.

The son was treated for smoke inhalation at a hospital and released.

The blaze melted the siding of two nearby homes and plastic and paint on cars. The intense flames also prevented firefighters from entering, said Johnson. It took firefighters from several towns three hours to extinguish the flames. Video of the fire showed the home being nearly entirely consumed by a fireball.

"Everything's being explored ... whether it was suspicious or not is still being investigated," Johnson said. He said a dog trained to detect accelerants was used at the scene, but he would disclose what the dog found.

Officials found Thomas Sullivan's body on the rear deck, where Johnson said he apparently landed after jumping from the second floor.

The fire, reported by a neighbor just before 2 a.m., left little behind of the family's home on a quiet street.

Johnson said no 911 calls came from inside the house, which he said was equipped with multiple wired smoke detectors. None sent any alarm to a monitoring station.

Sullivan was a former New York police officer assigned to the Bronx who had left the city for the comparatively tranquil suburbs two decades ago because he felt he could make a bigger difference in a smaller community.

"We are devastated, the village of Larchmont as a whole," said Larchmont Police Chief John Poleway, who said Sullivan was "full of integrity, honesty, he was dedicated to family."

Sullivan's daughters were students at Carmel High School. Mairead was a freshman and Meaghan a senior.

Principal Kevin Carroll said the girls "were good students and nice kids."

"Obviously today their teachers were very upset, and of course the other students," he said, adding that school psychologists were following the girls' class schedules to see the children who would be most upset.

He said that many of the students knew of the fire by the time they got to school, and that administrators made an official announcement at 7:10 a.m.

"It was very quiet for the most part," Carroll said of the school's atmosphere. "There was something in the air."

A funeral was planned for Saturday morning at St. James the Apostle Church in Carmel.