But at about 4:30 p.m. on Sunday, as her son Yakim McDaniels and a group of friends horsed around at 230 Lott Avenue, his clothing became entangled in a gate apparatus. He was lifted, then crushed at the top of the structure, witnesses said.

Emergency workers were able to extricate him, but he was pronounced dead at Brookdale University Hospital and Medical Center, the authorities said.

On Sunday evening, with candles burning at the base of the gate, Ms. Chase remembered the four words that the witness had told her: “Your son is dead.” She did not believe what she had heard.

“I still don’t believe it,” she said Sunday evening, as friends and relatives gathered to mourn with her.

Jamal Young, 28, who lives in the neighborhood, said the children had been trying to send the gate up and down, though it was unclear how they triggered its movement. A Fire Department spokesman said the gate, which allows entry to a parking lot and is approximately 20 feet high, could be opened either by a master key or by a sensor.

With Yakim suspended above, Mr. Young said, a crowd began to gather, summoned by the screams of onlookers. “He was hanging upside down from the gate,” Mr. Young said.

When Ms. Chase arrived, about 20 people had assembled, she said. Emergency workers had already arrived in an attempt to get Yakim free.

“There was nothing I could do,” Ms. Chase said.

Ms. Chase said her son was the second oldest of six children.

“He was a lovely person,” she said. “He never, ever got into trouble.”