A Uniondale man was arrested in Glen Cove after an off-duty police officer standing in line at a drugstore saw him trying to use a fraudulent credit card, police said.

After the clerk denied the man the purchase, he left, then returned and used a different credit card to complete a purchase Tuesday at the Walgreens at 93 Forest Ave., according to a news release from Nassau County police.

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Meanwhile, the off-duty Glen Cove officer had gone outside after seeing the failed attempt and notified police, the news release said.

Stephane D. Gentilus, 20, of McKenna Place was arrested by Glen Cove police as he attempted to drive away about 3:05 p.m., the news release said.

Gentilus had six fraudulent credit cards in his possession and an MSR X6 card reader/writer, police said.

The device can be used for legitimate purposes, police have said, but it can also be used to transfer data from a stolen credit card onto a different magnetic card.

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Gentilus was awaiting arraignment in First District Court in Hempstead on six counts of possession of a forged instrument and possession of a forgery device, Nassau police said.