Suffolk County Police said the incident happened in Miller Place shortly before midnight on Thursday, July 21.
The victim had arranged to meet another person in a parking lot on Route 25A to sell a Rolex watch.
At around 11:45 p.m. he was approached by three men, one of whom displayed a gun before robbing him of his watch, cellphone, and wallet, police said.
The men then fled in a white SUV, possibly a Mercedes Benz AMG GT with a rear spoiler, according to police.
The victim described the suspects as Hispanic. One was approximately 30 years old with light complexion, standing 5-feet-9-inches tall with a thin build, short hair and was clean shaven, police said.
A second suspect had a dark complexion, was short with a thin build, groomed beard and braided hair.
The third suspect was described as heavyset with a dark complexion, in his early 20s, approximately 5-feet-9-inches tall and clean shaven.
Police released surveillance footage showing one of the suspects along with a picture of the vehicle and watch involved.
Anyone with information leading to an arrest could be eligible for a crash reward from Suffolk County Crime Stoppers.
Anonymous tips can be called in to 1-800-220-TIPS or submitted on the Crime Stoppers website.
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