Surveillance video shows the suspect approach an employee at CND Automotive on Echo Avenue in Sound Beach with a gun.
It happened just before 9 p.m. on Saturday, October 19.
Authorities say he demanded the employee hand over the cash from the resister.
The employee handed over money, and the robber ran off.
Suffolk County Crime Stoppers offers a cash reward of up to $5,000 for information that leads to an arrest.
Anyone with information about these incidents can contact Suffolk County Crime Stoppers to submit an anonymous tip by calling 1-800-220-TIPS, texting "SCPD" and your message to "CRIMES" (274637) or by email at www.tipsubmit.com.
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