Meanwhile, fire officials now say the boy was "playing with fire."
According to the FDNY, the child had unwrapped a new toy, throwing the wrapping on the floor. An adult told the child to pick up the wrapping and throw it away. Instead, the child placed the wrapping on an open flame on the stove.
The stove was on, the spokesman said, to provide heat to the apartment. There was no explaination as to where the adult then went or why they did not notice.
Seeing the packaging on fire, the child somehow then took the burning paper off the stove and placed it under a bed and the fire became involved, the fire spokesman said.
The spokesman also says the FDNY now knows Martinson was "low on air" in the final moments of his life.
Martinson, who was a supervisor, would have been one of the last firefighters out because it was his job to make sure everyone else was out. Fire officials are not sure why he didn't get out. That is currently under investigation.
Martinson died while trying to save residents from a burning apartment building in Brooklyn. It happened at a high rise on Bedford Avenue in Crown Heights, Brooklyn, Thursday night.
The fire sent smoke coursing through the building, forcing frightened residents to take refuge in their apartments rather than risk fleeing through the blackened hallways, officials and residents said.
Martinson, 40, was found unconscious in the apartment where the fire began, a building on the site of the former Ebbets Field.
"He gave everything he had," Mayor Michael Bloomberg said late Thursday at Kings County Hospital Center. "His death really breaks the hearts of all of us. Telling the wife that her husband's not going to come home again is not an easy thing; it's very sad."
The couple has a 22-month-old son, and Martison's widow is pregnant.
"These children will grow up never knowing their father," Bloomberg said.
Martinson was among more than 100 firefighters called to the 25-story building in the Ebbets Field Houses complex, named for the ballpark that was once home to the Brooklyn Dodgers.
The cause of the fire was under investigation on Friday.
Residents in the 14th-floor apartment had left the front door open, and that let smoke flow out into the 400-apartment building, Bloomberg said.
Ten stories away, on the 24th floor, the smoke was so thick in the hallway that resident Basil Patrick turned back after opening his door.
"It's black out there," Patrick, 56, said by telephone Thursday evening.
Simon Black said flames shot from the burning apartment's windows while smoke surged into the hallway.
"I don't know how they got in there," Black, 37, said of firefighters. "They're supermen."
Martinson was a police officer for four years before joining the Fire Department in 1993. His late father had been a member of the department, and "he always wanted to be a firefighter like his father," said Thomas DeLisio, a longtime neighbor of the family's on Staten Island.
Martinson, his wife, Jessica, and their son, John Patrick, recently moved into what had been his grandfather's house, DeLisio said.
"It's a heartache," the neighbor said.
Martinson was the first city firefighter to die in the line of duty since Aug. 18, Robert Beddia and Joseph Graffagnino were trapped in a blaze in the condemned former Deutsche Bank building at ground zero. On June 21, Daniel Pujdak fell to his death from a ladder near the top of a four-story Brooklyn building where he was tackling a fire.
