Three youths escaped a house on fire on Twomey Avenue in Calverton this afternoon. Riverhead Fire Department volunteers brought the fire under control within a half-hour. One of the youths, the son of the homeowners, said he heard what sounded like shotgun shells going off in the attic. He said he called 911. All three safely evacuated the home without injury. Twomey Avenue resident Mario Sequen also said he heard what sounded like explosions or gunshots. “I heard pop-pop-pop and then I saw the sky filled with smoke, so I called 911,” he said. Riverhead police officers responding to the 911 calls at 1:31 p.m. were first on the scene at 184 Twomey Avenue. Police immediately shut down Twomey Avenue between Manor and Deep Hole roads because there is a natural gas main in the road. RFD responded with seven pieces of apparatus and about 75 firefighters. The Riverhead fire marshal is on scene beginning his investigation. Riverhead Fire Chief Joseph Raynor declared the fire under control at 1:56 p.m.