The Coffee Crook is at it again.

Two more Dunkin’ Donuts shops — in Burlington and Bedford — were robbed Monday night, bringing the tally to 21 Dunkin’ shops robbed in the state since March.

At about 8:20 p.m. Monday, a Dunkin’ store at 28 Winn St. in Burlington was held up. A man dressed in black with a handgun entered the store and robbed it, then fled on foot, Burlington police said.

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About 20 minutes later, police responded to the Dunkin’ shop at 308 Great Road in Bedford for a report of an armed robbery. A masked man with a handgun entered the store through a drive-up window and demanded money from the two employees there, Bedford police said.

“As the suspect walked over to the registers, the two employees were able to flee out the back door to a neighboring business,” said Bedford Police Chief Robert Bongiorno. Once in the neighboring business, the two Dunkin’ employees called 911, police said.

On surveillance video, the suspect is seen attempting to extract money from two cash registers, then fleeing on foot, police said.

When Bedford police arrived, they deployed a K-9 unit from Billerica, which lost the track of the suspect about a block from the store.

Police didn’t release how much money the suspect got away with.

Bedford and Burlington police are working together to determine if the two robberies are connected. Police also believe a third robbery Monday night — at a Hess gas station in Waltham — might be connected, and are coordinating with police there, Bongiorno said.

“The timeline would match up between all three robberies,” Bongiorno said. “Once we determine whether the robberies were or were not related, we will then reach out to the other agencies and expand the scope of the investigation.”

A number of similarities exist between all 21 Dunkin’ robberies, though police have only officially connected five of them so far.

In every case, the suspect has brandished a gun or a knife, and he has frequently worn dark clothing. All the robberies have occurred on a weeknight, and all but one have occurred between 7 p.m. and 11:30 p.m.

In one of the robberies, in Raynham in August, the suspect entered the store through the drive-through window, as in Monday night’s holdup in Bedford.

Dunkin’ Donuts has offered a $10,000 reward for anyone with information regarding the robberies.