The as-yet-unidentified 68-year-old man jumped in front of the A train around 6:45 a.m. at 80th Street in Ozone Park, the NYPD said.
The department summoned the bomb squad and shut down the area after responders reported finding the "suspicious device" -- described as a pipe capped at both ends -- in his backpack.
It was later deemed safe.
The man was taken in critical condition to Jamaica Hospital Medical Center in Richmond Hill, they said.
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