BOSTON (CBS) – Boston’s top cop says his department is “disturbed” after an 11-year-old was one of three juveniles arrested this week in a series of armed robberies.

A 13-year-old and 16-year-old were also arrested and charged with armed robbery (knife). All three boys are from Dorchester.

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Police said there have been several recent armed robberies at knifepoint in the Columbia Road and Ceylon Street area. They arrested the boys Wednesday at about 3 p.m. following an investigation and surveillance of the area, and found a knife on one of them.

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The three were arraigned Thursday in Boston Juvenile Court.

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“An 11-year-old—it’s sad,” Police Commissioner William Evans said in a statement. “We’re disturbed when we see kids this young committing crimes, but hopefully this is a wake-up call for the kids, their families, the community, and for us as a police department. Now we can work together, get in touch with these kids, provide them with services, and try to get them on the right track.”