Detectives are currently seeking that person but offered few other details.
He is always wearing a mask when he breaks the subway windows, they said.
"We are very confident we will make an arrest in that pretty soon. We believe he is using a hammer to break the windows," Chief of Detectives Rodney Harrison said.
Police last week released surveillance video that shows the alleged suspect.
RELATED | Man suspected of vandalizing 63 subway cars, breaking 200 windows in NYC
Since May, more than 400 windows have been smashed on subway cars, including hundreds on 7 trains alone.
The MTA says the damage has cost them more than $300,000.
So many windows have been broken that the MTA is running out of replacements.
RELATED | Subway window-smashing spree: 7 train vandal strikes again, service at risk
The MTA is offering a $10,000 reward in the case.
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