NEW YORK (CBSNewYork) — The NYPD has made what it expects will be the first of multiple arrests in the brutal sucker-punch attack on a 57-year-old woman on the Upper West Side earlier this month.

Police picked 18-year-old Trinity Velez of the Bronx on robbery charges in connection to the Oct. 17 incident.

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Surveillance cameras caught one of the attackers hitting the woman in the head from behind and knocking her to the ground.

The Guardian Angels later posted fliers with images of the suspects.

The brazen attack took place at 69th Street and Amsterdam Avenue, a quiet neighborhood filled with co-ops and condo buildings, in a section of the sidewalk that is enclosed by scaffolding due to high-rise construction, police said.

What the attackers didn’t realize was that their every action was being recorded by a security camera in the construction shed.

The other suspect is seen trying to pull the woman’s purse away from her, but they ran away empty-handed when the victim refused to let go of it.

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The victim suffered facial fractures, police said.

In addition to the two suspects involved in the attack, police have also released images of two additional persons of interest.

(Credit: NYPD)

It was the second of two such attacks in the city within a week. Police said a man sucker-punched a 68-year-old woman standing with use of a cane outside her home on 137th Street and Adam Clayton Boulevard in Harlem during the early morning hours of Oct. 12.

The woman was leaning against a wall smoking a cigarette when a man walked up and clocked her in the head. No words were ever exchanged, police said.

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Anyone with any information about this incident is asked to call NYPD’s Crime Stoppers hotline at 1-800-577-TIPS (8477) or 1-888-57-PISTA (74782) for Spanish. You can also submit a tip via the Crime Stoppers website, by Tweeting @NYPDTips or by texting a tip to 274637 (CRIMES) and then entering TIP577.