New York City ? A 6-year-old boy’s attempt to hide burning gift wrap paper from his mother caused the fire in a 25-story Brooklyn high-rise that killed a veteran New York City firefighter, fire officials said Friday.

Lt. John H. Martinson, 40, of Staten Island, was found lying on the floor about 10 feet inside the apartment and taken to Kings County Hospital Center. He died of smoke inhalation and thermal burns, the city medical examiner’s office said.

The fire started when the boy, asked by his mother to clean up wrapping paper, put the paper on top of burners of a gas stove being used to heat the apartment, fire officials said. When the paper ignited, the boy grabbed the burning trash and hid it underneath his bed, officials said. The mother evacuated the boy and another child and left the door open, causing fire and smoke to pour into the hallway, which made it difficult for firefighters to reach the source, officials said.