Last Updated 11:35 a.m. ET
BOSTON - A 6-alarm arson fire tore through a large apartment building, including the apartment of a couple on the third floor who dropped their young grandson into the arms of a waiting firefighter, officials said.
A man who came to a hospital with burns and claimed he started the fire was arrested, police said.
The explosion and fire may have been the result of a failed suicide attempt, according to a preliminary police investigation.
Firefighters rescued at least 15 people, including the 6-year-old grandson of Herbert and Judith Lamb, who live on the third floor of the apartment building and said they were woken by an explosion and smoke.
The Lambs broke a window and dropped their 6-year-old grandson into the arms of waiting Boston firefighters.
"I had to drop him out the window," Judith Lamb told The Boston Globe. "The firemen caught him."
Boston Fire Lieutenant Glenn McGillivray told the newspaper he was the one who caught the child.
"I knew she wouldn't be able to hold him until we got help, so they dropped him, and I caught him in my arms from the third floor," McGillivray said. "Thank God I caught him. I've never had to do that before, and I hope I never have to do it again."
He said firefighters used a ladder to rescue Judith Lamb.
The blaze damaged or destroyed more than two dozen apartments in the large, U-shaped building on Wardman Road in the city's Roxbury neighborhood.
CBS Station WBZ reports that a man walked into Boston Medical Center with third-degree burns and confessed he started the fire by tampering with a gas line in his apartment. He was arrested and charged with arson.
The man's name was not immediately released. It was not clear if he lived in the building or was visiting, fire department spokesman Steve MacDonald said.
Police have not released his name, but police spokesperson Elaine Driscoll said he may have been trying to kill himself. Police stressed that the investigation is ongoing.
He is now being treated in the burn unit at Massachusetts General Hospital.
Residents who escaped said they heard an explosion at about 1 a.m.
MacDonald said the windows and frame were blown out in one corner of the building and bricks were littering the street.
Ten residents of the building were taken to hospitals, most suffering from smoke inhalation. Two firefighters and a police officer were also treated for what were believed to be minor injuries, MacDonald said.
Firefighters said all residents were accounted for, though MacDonald cautioned that crews had not yet been able to enter the building.
About 160 firefighters were called to the scene and they were still pouring water on the building several hours after the blaze started.
A temporary shelter was set up in the city for residents displaced by the blaze.