Yakim McDaniels was with friends when his clothing became entangled in the gate of the Brooklyn borough parking lot as it rose, taking him with it and crushing him at the top, The New York Times reported.
Authorities said the youth was cut free by emergency workers but was pronounced dead at an area hospital.
"I still don't believe it," said his stunned mother, Doris Chase, 33, who arrived moments after the accident.
"There was nothing I could do.
"He was a lovely person. He never, ever got into trouble."
A neighbor, Jamal Young, 28, told the Times the kids had been trying to send the 20-foot-high gate up and down, and somehow triggered its movement. A city fire department spokesman said the gate could be activated by a master key or by a sensor.