AYER — A man brandishing a black handgun allegedly robbed the Gulf gas station at 52 Park St. Sunday night.

Wearing a black ski mask, the man held up the store around 10 p.m., said Lt. Brian Gill of the Ayer Police Department. He allegedly demanded money from a woman employee who was the only clerk on duty. No one else was in the store at the time.

The robber made off with about $500 and fled on foot, Gill said.

Police are analyzing video-surveillance footage for photos of the suspect, as well as following up on possible leads.

The armed robbery is the third one so far this year, Gill said.

“Definitely, it’s an uptick from last year,” he said, citing the economy as a possible reason for the increase.

The suspect is described as 5 and a half feet to 6 feet tall, and he was last seen fleeing the area in a hoodie and ski mask.

If anybody has information, contact Ayer Police Det. Kellie Barhight at 978-772-8200, ext. 507.

— Joyce Tsai