The 51-year-old man was hit by the southbound bus as he crossed Fifth Avenue at 59th Street just before 6 p.m. Tuesday.
He was taken to New York-Presbyterian-Cornell Hospital in critical condition.
The victim was possibly struck by an MTA bus, based on witness accounts, but investigators were not immediately able to locate a bus that matched the witness description.
It was also unclear if the driver was even aware someone had been struck.
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