An armed robber struck a convenience store clerk in the head with a firearm during a robbery in Tewksbury early Thursday morning, according to authorities.
Police responded to the report of the incident at Circle K on Route 133 around 2:30 a.m. Thursday morning.
The assailant, about 5-foot-9 with a stocky build, wore a mask, latex gloves, a black hooded sweatshirt, black shorts and white sneakers, Tewksbury police said.
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The condition of the store clerk is unclear.
The case in under active investigation.