State Police released a summary of the events that led to the death of bombing suspect Tamerlan Tsarnaev and the closing of metro Boston communities as law enforcement searched for his younger brother.In a statement, police said the first indication of trouble was 10:24 p.m. when MIT Police received a call from someone reporting they had heard what they feared was gunshots. Four minutes later, the 7-11 store at 750 Massachusetts Avenue was the victim of an armed robber =- but that crime was not commited by the brothers, State Police now say.One minute later, however, authorities allege that the brothers did shoot and kill MIT Police Oficer Sean A. Collier as the officer sat in his MIT cruiser.Two minutes later, authorities receive a call that a car has been carjacked by two men outside 816y Memorial Drive. A short time later it was not immediately clear a Transit Police officer spots the vehicle and pursues, a chase that came to a stop in Watertown.In the moments that followed, 200 rounds were fired by police and apparently by the brothers. Police also recovered numerous pieces of evidence including evidence of homemade explosives, including pipe bombs and another pressure cooker, State Police said.Also, contrary to what Alben said earlier this afternoon, no potential explosives were found on Norfolk Street in Cambridge where the two brothers lived, and a planned controlled explosion was deemed unwarranted.We did not have to do the controlled detonation, State Police spokesman David Procopio wrote. We thought a car there might have an explosive but it did not.