Norwalk, Conn. officials also said Boston police asked them to search an Amtrak train that left South Station in Boston at about 5 a.m. Friday.
Police from Norwalk, Stamford and the Metropolitan Transportation Authority boarded the southbound train in East Norwalk with at least one bomb-sniffing dog shortly before 8:30 a.m., but didn’t find anything.
The suspects’ clashes with police on Thursday night began only a few hours after the FBI released photos and videos of the two young men, who were seen carrying backpacks as they mingled among marathon revelers.
The bombings on Monday killed three people and wounded more than 180 others, and authorities revealed the images to enlist the public’s help finding the suspects.
Exactly how the long night of crime began was marked by conflicting reports.
Police initially said the brothers robbed a 7-Eleven convenience store in Cambridge, near the campus of the Massachusetts Institute of Technology, but they later said the robbery there was committed by someone else.
A surveillance photo released by authorities of Dzhokhar Tsarnaev came from a gas station where the suspects stopped.
They then shot to death an MIT police officer while he was responding to a report of a disturbance, investigators said.
“They encounter an MIT police officer and rather than see, ‘Is he going to follow us? Is he going to chase us?’ it appears that they came up and engaged him, killed him in his police vehicle, took off,” CBS News’ Miller said.
The officer died of multiple gunshot wounds. The Middlesex County District Attorney’s Office identified the MIT officer as 26-year-old Sean Collier, who had worked at MIT since January 2012.