<P> Massachusetts Bay Transportation Authority Police Officer Richard H. Donohue Jr. was also critically wounded but survived . Boston Police Department officer Dennis Simmonds was injured by a hand grenade and died April 10, 2014 . Fifteen other officers were also injured . A later report by Harvard Kennedy School's Program on Crisis Leadership concluded that lack of coordination among police agencies had put the public at excessive risk during the shootout . </P> <P> Only one firearm was recovered at the scene, a Ruger 9 mm pistol with a defaced serial number . </P> <P> The men were identified via registration records on their Honda at the scene, as two brothers whose family had immigrated to the United States seeking political asylum around 2002: 26 - year - old Tamerlan Tsarnaev and 19 - year - old Dzhokhar "Jahar" Tsarnaev . The FBI released additional photos of the two during the Watertown incident . Early on April 19, Watertown residents received reverse 911 calls asking them to stay indoors . On the morning of April 19, Governor Patrick asked residents of Watertown and adjacent cities and towns to "shelter in place". Somerville residents also received a reverse - 911 call with orders to shelter in place . </P> <P> A 20 - block area of Watertown was cordoned off and residents were told not to leave their homes or answer the door, as officers scoured the area in tactical gear . Helicopters circled the area and SWAT teams in armored vehicles moved through in formation, with officers going door to door . On the scene were the FBI, the Bureau of Alcohol, Tobacco, Firearms and Explosives, the Department of Homeland Security, the National Guard, the Boston and Watertown Police departments, and the Massachusetts State Police . The show of force was the first major field test of the interagency task forces created in the wake of the September 11 attacks . </P>

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