NEW YORK (CBSNewYork) – The NYPD is now looking for four suspects caught on camera in a violent attack on the Upper West Side.

Surveillance cameras caught one of the attackers sucker-punching a woman in the head from behind and knocking her to the ground.

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The Guardian Angels have posted fliers with images of the suspects who police say attacked the woman Thursday night.

It happened on 69th Street and Amsterdam in a section of the sidewalk that is enclosed by scaffolding because of high rise construction.

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 woman refused to let go of her purse.

The 57-year-old suffered fractured bones on her face.

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

(Credit: NYPD)

This brazen attacked happened on a quiet stretch of the Upper West Side filled with co-ops and condo buildings.

People who live in the area told CBS2 they will now avoid walking through the construction shed and will cross Amsterdam Avenue instead because they don’t feel safe.

“I’ve walked through many times and I’ve never had any kind of problem. I’ll be more aware now,” one person told CBS2’s Matt Kozar.

NYPD Chief of Detectives Dermot Shea tweeted that police are offering a $2,500 reward for information leading to the suspects’ arrest.

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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.