April 18, 2013
5 p.m.: The FBI releases photos and videos showing two men they describe as suspects in the Boston Marathon bombings.
11 p.m.: Police respond to a call on the campus of the Massachusetts Institute of Technology, where university police officer Sean Collier, 26, has been shot. He dies from his injuries. Police later say they believe the bombing suspects were responsible for the shooting.
April 19, 2013
Tsarnaev dies after a shootout with police in Watertown, Massachusetts. Hours later, investigators reveal that he and his 19-year-old younger brother are the marathon bombing suspects.