NEW YORK (AP) — A badly charred note with the words “am sorry” was discovered Friday in the torched apartment where investigators suspect a teenager killed his mother and siblings before committing suicide, police said.

New York Police Department spokesman Paul Browne said the note — with only fragments of words and sentences still legible — was found along with a melted butane lighter in the Staten Island home. It was being analyzed to try to determine who wrote it and if it had any significance.

The bodies of Leisa Jones and three of her children were found in their torched apartment early Thursday morning. Her fourth child, a 2-year-old boy, was pulled out alive but died later at the hospital.

WATCH NBC NEW YORK COVERAGE HERE:

Authorities were awaiting the results of autopsies Friday on Jones, her daughters and her teenage son. An autopsy on 2-year-old Jermaine Sinclarie determined that he died of smoke inhalation, Browne said.

Browne said detectives had questioned the younger boy’s father, who was in Baltimore at the time of the fire, but he was not considered a suspect. The other children have different fathers, he said.

The girls were identified as 10-year-old Brittney Jones and 7-year-old Melonie Jones. The 14-year-old son, known previously as C.J. Jones, had tentatively been identified as Raymond Romoy, Browne said.

Police were investigating on the theory that the deaths were the result of a murder-suicide committed by the older boy, who had a history of playing with fire.

The girls’ throats were slit. Their bodies were found along with that of their mother and the 2-year-old in the front room of the family’s second-floor apartment. The teenage boy’s body was found slumped over a bed in a back bedroom, police said. A straight razor was discovered underneath his body.

The teenage boy recently had been seen setting a fire at a public pool, and neighbors described him lighting paper on fire in front his apartment building in recent days, police said.

Firefighters said they believed the blaze was intentionally set, but their investigation was continuing.

Neighbor Raquel Fagone said she spotted the teenager lighting scraps of paper in front of the building a few months ago.

“I told him not to do that, and he put them out,” Fagone said.

Then, early Thursday, she heard a commotion in the family’s apartment, directly above hers.

“It sounded like a little child running, upset, in distress, upset, screaming, running around,” she said. “I heard a bang and a kind of kaboom.”

Fire officials say the fire started in the apartment and moved through the two-story building’s attic space and roof. The tenants in the other three apartments got out safely.

The 32-year-old Jones was from Trinidad and attended a beauty school during the day, neighbors said.

Copyright 2010 The Associated Press.