A child is fighting for his life after he fell down an elevator shaft in his apartment building located on Grand Concourse.

Police say 6-year-old Matthew Mendoza is still at Harlem Hospital in serious condition. Mendoza is undergoing surgery from a fractured skull.

According to his family, Matthew has special needs and he was being watched by his grandfather and a home aide when he managed to slip out of the apartment and climb six flights of stairs, all the way to the roof of the building.

Police say there was a gap between the wall and floor that was just big enough for Matthew to slip through. He then fell down the elevator shaft, but at this time it's unclear how many stories he fell.

The FDNY says they later found him unconscious on top of the elevator in the basement and rushed him to the hospital.

Matthew’s grandfather Segundo Campoverde told News 12 that the child often sneaks out of the apartment and that the family has installed three locks on the door, but somehow he still managed to escape.

The Department of Buildings is now investigating the incident.

In the meantime, officials say they've issued a cease use order on the elevator and are working with the elevator service company to conduct a full inspection.

 Signs were placed on the door that say no one is allowed onto the roof but both of the doors were unlocked and not hard to open.