CAMBRIDGE (CBS) – A robber forced his way behind the counter of a Cambridge ice cream store, cleaned out the register and stole the tip jar.

The owner of the Emack & Bolio’s in Porter Square believes the robber had a gun. This is the second time in a month the store has been hit.

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Surveillance video shows the man forcing a woman working there to open up the register.

“Made his way behind the counter and took the cashier, had her open up the register and got away with cash,” said Jeremy Warnick, spokesman for Cambridge Police.

Police say the suspect never showed a weapon, but motioned to his waistband.

The store was also hit one month ago. Now customers are offering support.

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“I heard about their robbery, and I remembered about the first one, and then they got hit again, and I came and told her we support you guys and I’m really sorry what happened and it’s not fair,” said customer Donna Stone.

Police believe the two robberies may have been committed by the same suspect, a white man in his 40’s or 50’s wearing a baseball cap. He fled towards Somerville.

They say the heartless thief even cleaned out the tip jar.

“That’s what you know, concerns us,” Warnick said. “To be just about a month after and for them to come back, and this time it was at nighttime.”

“They have the gall to do it, they’re going to try again until they get caught and I hope they do get caught,” said customer Flora Valente.

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Police say no one was hurt during either robbery.