On Friday, November 18, 2011 at approximately 5:20 PM Billerica Police Officer Donald MacEachern observed a stolen 2011 Nissan Murano operating on Route 3A in North Billerica. Officer MacEachern had been aware of an earlier alert for this vehicle which indicated it had been used during an armed robbery.  The robbery occurred at the Brite Clean Cleaners in Chelmsford the previous day. Officer MacEachern was also aware that the suspect in that case was a young white male with a goatee that was wearing a black hoodie sweatshirt with white lettering. The suspect had also been suspected of a similar armed robbery on Middlesex Turnpike in Burlington on November 15. In that robbery, a female clerk working for Dunkin Donuts was threatened at gun point for the money in the store’s register. Having this knowledge in mind, Officer MacEachern conducted a tactical felony stop of the vehicle and arrested the driver for possession of a stolen motor vehicle and operating with a revoked license. Officer MacEachern also located a replica semi-automatic hand gun believed to have been used in the previous robberies. The individual arrested was identified as Derek Colamartino, a 21 year old male formerly of Billerica. Based on evidence collected following his arrest, the Burlington Police Department subsequently charged Mr. Colamartino with the armed robbery of their Dunkin Donuts on November 15, 2011. The investigation into the Chelmsford armed robbery remains open at this time.