The boy, named Jose, plunged from the bedroom window in the city's Westchester Square section just after 1:30 p.m.
"I went out like, where's the baby, where's the baby?" his sister, Mia Jiminez, told WABC-TV in an exclusive interview. "The baby was right there. He was with his iPad."
The boy had pushed out a piece of cardboard next to the air conditioner, and the remaining space was wide enough for him to slip through.
Jose struck a store awning -- which likely saved his life -- before landing on the ground.
SEE ALSO: Florida school principal seen paddling young girl in disturbing video
"I just saw the little boy crying hysterically and a lot of blood going down his rib cage," witness Elias Peralta said.
He was taken to an area hospital with a contusion to the head, a broken right femur and other injuries. Miraculously, he is expected to survive.
Mia, his mother and his aunt were all home at the time of the fall.
"My heart is broken because we are always aware of where he is," said his aunt, Rosmary Santelises. "And in one minute, it happened so fast. He's the angel in the house."
At first, no one in the apartment realized Jose had fallen out of the window until a neighbor came banging on their door.
That's when they ran downstairs and saw Jose, who had tried to stand up several times.
"I saw him, he moved, I'm like thank God," said the boy's mother. "I take him, I was crying, my friend was like, 'Don't cry, he's alive.' He was so lucky."
The city's Administration for Children's Services was notified, but no criminality is suspected.