Police are investigating a robbery at Green Acres Mall involving people who met on social media.

The victim, a 29-year-old man, arranged through the letgo website to sell clothing to two people at the mall on Sunrise Highway in Valley Stream, Nassau County police said. Letgo calls itself as “the app that lets you buy and sell quickly.”

The first suspect asked the victim to see the items. When the victim bent down to get them from his book bag, the suspect and another suspect “began to punch him in his face and body,” police said.

The first suspect took the bag containing the merchandise and fled south on Mayfield Lane, police said.

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The victim declined medical attention.

Fifth Squad detectives urge anyone with information about the crime to anonymously call Nassau County Crime Stoppers at 1-800-244-TIPS.