Boston Marathon Bombers are confronted by police in Watertown.

Shortly before 9:00 p.m., brothers Tamerlan and Dzohkar Tsarnaev, Cambridge residents and Chechneyan immigrants, engage in a shootout with law enforcement officers. Boston police officer Dennis “D.J.” Simmonds is wounded, Tamerlan is killed, and his younger brother Dzohkar is arrested the next day. He is subsequently tried at the Moakley Federal Court House, convicted of multiple counts of murder on April 8, 2015, and sentenced to death on June 24, 2015.