Troops were also deployed to key locations, such as Buckingham Palace, the prime minister's residence at 10 Downing Street and Parliament.
British Dr. Mounir Hakimi is all too familiar with innocent children being killed by bombs. He just never thought it would happen so close to home.
Olivia Campbell joins eight-year-old Saffie Roussos and Georgina Callander,18, among the first victims of the attack be identified.
Split-second decisions during the terrifying moments after a suicide bomber targeted Ariana Grande fans transformed many regular people into heroes.
Ariana Grande's fans are predominantly teens and young girls, and many had gone to the venue for a night of fun that turned into a scene of carnage.