Law enforcement sources told WCBS-TV and WNBC-TV Jeffrey Babbitt, a 62-year-old retired railroad conductor, was declared dead at Bellevue Hospital.
Police said they expected to upgrade charges against his alleged assailant, Lashwan Marten, 31, WCBS-TV said its sister station WINS-AM reported.
Babbitt was assaulted Wednesday afternoon while walking in Union Square when Marten allegedly announced his violent intentions and then carried through on them.
"He said 'the next white person who walks by I'm going to [expletive],'" WCBS-TV quoted one woman as saying. "His fist went in and the man's head bobbed and he hit the ground and you could hear his skull hitting the ground."
Marten attacked two other people before police arrived, witnesses said.
Babbitt was the primary caregiver for his 92-year-old mother, WCBS-TV said.
"Jeffrey was a kind & gentle soul. May he rest in peace," a note posted on an elevator in Babbitt's apartment building said.
Marten also is accused of punching a 48-year-old person and an 18-year-old, both also white, WNBC-TV said. Those two victims were treated and released.