> To listen, go to bostonglobe.com/soundtrack. Friday, April 19. Day breaks on a terrorized city. Bombers had struck the beloved Boston Marathon just days before. After a fierce early morning firefight between police and the two suspects, the surviving brother, 19-year-old Dzhokhar Tsarnaev, escapes into the residential streets of Watertown. The city, like much of Greater Boston, is on lock-down. SWAT teams go house to house. Typically bustling streets and storefronts are deserted. Unnerved residents peer warily through their windows, waiting for it to end. Hours pass this way, children, parents, seniors — everyone — trapped inside on a warm spring day. Finally, at nightfall, there is news: Tsarnaev is taken into custody, found hiding in a boat being stored in a backyard. The siege is over. Watertown breathes a collective sigh of relief, and then relief turns to jubilation. Dozens of residents gather in Watertown Square to celebrate: the work of the police, their return to freedom, the end of a surreal and awful week in April. They chant “USA! USA!” and “Watertown! Watertown!” They scream and cheer for police cars and motorcycles, their blue lights ablaze. The honking of passing cars fills the night. A good end to a bad day.