It happened Thursday afternoon on East 47th Street and Third Avenue.
Police now say they've arrested 28-year-old Christopher Guzman of Manhattan on assault charges.
He allegedly ran up behind the 51-year-old woman and struck her in the back of the head.
Sources say the victim is Lisa Cavanaugh, a staffer with Gov. Andrew Cuomo's office in New York City. She's been hospitalized.
"Lisa is a valued member of Team Cuomo and we have been in constant touch with her and her family to make sure she has everything she needs in her recovery. We thank the NYPD for their quick work in apprehending the person they believe attacked her," said Rich Azzopardi, a senior advisor to Gov. Cuomo, in a statement to CBS2.
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