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He had wandered onto the Brooklyn subway tracks near Hoyt Street Station on Thursday morning, a boy of about 12, unattended and willing to test fate.

He managed to amble over the rail that carries 600 volts of electricity and wedge himself between the columns that separate the local and express tracks.

It was about 9:15 a.m., and a northbound train was barreling his way.

The response was swift. A customer hurried to a call box and pushed a button for help. The station agent who got the call notified the rail control center. All train operators in the area received an alert and were told to be on the lookout.

By then Hopeton Kiffin, a 51-year-old operator for the No. 5 train, had already spotted a flash of red on the tracks ahead of him in an area his express train would normally rush through. He slowed the train down. Someone on the platform pointed. There stood a boy in a red shirt, staring straight ahead, clapping his hands.