REVERE – A gun-wielding robber was arrested Tuesday when police burst into the Walgreens on Broadway and stopped him in the act, police said.Kevin Gochakowski, 17, of 105 Gore Road, Revere, was arrested and charged with armed robbery while masked shortly after the 1:20 a.m. hold-up.Revere Police Sgt. Glen Malley and Officer Robert Impemba were about one block away from the drug store when they received a report of a robbery, police said.Within 30 seconds, the officers went into the store with their guns drawn and ordered Gochakowski to the floor, according to police.Gochakowski had a T-shirt tied around his face and was pointing a weapon at the cashier when the officers burst in, police said.He was standing behind the counter waiting for the cashier to give him money when he complied with the officers’ orders to drop to the floor, police said.Police said the weapon that Gochakowski was holding turned out to be a BB gun, but closely resembled a semi-automatic handgun.