Orlando: Inside the Deadliest Mass Shooting in US History

It is the deadliest mass shooting in the United States and the worst terror attack since 9/11. Forty-nine people are dead and even more left injured after Omar Mateen opened fire on Pulse Nightclub in Orlando this weekend. The shooter, previously investigated by the FBI in 2013 and 2014, has been confirmed by law enforcement to have pledged his allegiance to ISIS.