Larchmont police captain Thomas Sullivan, Sr., his wife Donna and their teenaged daughters Meaghan and Mairead all died whe flames swept through their home in Carmel.
The Sullivan's son, Thomas, Jr., was the lone survivor.
Investigators determined ash from a cigarette smoked by the younger Thomas caused the fire.
It was ruled an accident.
All the victims died from breathing smoke and carbon monoxide as their home was consumed by flames.