Developing fast as they say in the news business. (H/T Instapundit)With a bomb strapped to his chest, one of the Boston Marathon suspects was killed early Friday after he and his accomplice robbed a 7-Eleven, shot a police officer to death, carjacked an SUV and hurled explosives out the window in an extraordinary firefight with law enforcement, authorities told NBC News.The second suspect — the one in the white hat in photos released by the FBI — was on the loose, and police ordered people in the Boston suburb of Watertown to stay in their homes and businesses not to open. Boston shut down its buses and subway system for the hunt.The suspects are brothers with the last name Tsarnaev, law enforcement officials told NBC News. The suspect on the loose is 19 and has a Massachusetts driver’s license, they said. Law enforcement officials told NBC News that both men had international ties, had been in the United States about a year and had military experience.