latest new story (Boston bombs)

Our latest roundup news story, from Ed Pilkington and Adam Gabbatt in Boston and Miriam Elder in Moscow, has a blow-by-blow account of events overnight that have led to today's standoff: In what law enforcement officials described as an ambush-style attack, Sean Collier, 26, was shot multiple times at about 10.30pm as he sat in his police cruiser within the MIT campus. Tamerlan Tsarnaev died after an ensuing car chase that ended with a shootout in the suburb of Watertown, but his younger brother managed to break through the line of officers and escape. An officer with the Massachusetts Bay Transportation Authority was wounded. Hundreds of officers are now amassed in Watertown, supported by bomb squad robotic equipment and armored vehicles, giving the quiet town the appearance of a war zone. Across the greater Boston area, almost a million people remain confined to their homes, mass transit systems are suspended and a no-fly zone has been imposed as the hunt for the fugitive continued.