The 14-year old survivor was among as many as a dozen people inside the house when the smoke started to spread and fire started to consume it.
Somehow, none of them noticed the fire until Gilbert Encarnacion pounded on the door, and family members started rushing out.
"When I asked the owner, she was screaming there are two kids in the garage. There's two kids missing," Encarnacion said.
Suffolk County police say they responded to the fire on Spur Drive North in North Bay Shore at 8:30 p.m. Monday.
Smoke and fire was still rising from the rear of the house when they arrived.
"We were notified by the occupants that there were two people trapped inside," Brentwood Fire Chief Eric Raudies said. "They were located and removed."
Firefighters found 17-year-old Luis Zayas and Angela Alvarez, 16, unconscious in a ground floor bathroom. They were taken to a hospital, where Zayas was pronounced dead.
Alvarez was listed in critical condition suffering from smoke inhalation and burns.
Throughout the day, friends grieved as family members salvaged what they could of their belongings.
Investigators discovered this house was no normal single family home.
"It also appears to be an illegal multifamily at this time," Lawrence O'Leary said.
O'Leary, Islip's code enforcement chief, says the home had been illegally subdivided into as many as three apartments with a common exit. The garage, in which the teens were trapped, was actually their home, complete with makeshift power cords, running exposed outside the house.
Investigators said a wall inside a converted garage delayed firefighters trying to reach the victims.Authorities believe the fire case caused by faulty wiring.
Police say their investigation could result in a criminal charge.