The victim is a member of Gov. Andrew Cuomo's staff.
Officials say the suspect followed the 51-year-old woman on East 48th Street just after 2 p.m. Thursday as she left the governor's office.
Police say the man approached her form behind and hit the woman in the back of the head with a cinder block before fleeing westbound on East 48th Street.
The NYPD said it was an unprovoked attack.
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The victim suffered injuries to the back of her head. She was taken to Bellevue Hospital in serious but stable condition.
The suspect was identified Friday morning as 28-year-old Christopher Guzman. He is facing a charge of assault.
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