A large truck loaded with guns and hand grenades drove into a crowd of people who gathered for a Bastille Day fireworks show Thursday in the southern French city of Nice killing at least 70 people and injuring 100 more in a terror attack, officials said Nice Mayor Christian Estrosi confirmed the death toll in a post on Twitter, calling Thursday "the worst tragedy in the history of Nice." Estrosi also asked residents to stay indoors immediately following the attack