Fifty people were killed inside Pulse, a gay nightclub, Orlando Police Chief John Mina and other officials said today, just hours after a shooter opened fire in the deadliest mass shooting in U.S. history. At least 53 more people were injured, Mina said. Police have shot and killed the gunman, he told reporters. "It appears he was organized and well-prepared," the chief said, adding that the shooter had an assault-type weapon, a handgun and "some type of (other) device on him." Officials warned that a lengthy investigation was ahead, given the number of victims and the scope of the violence. "There's blood everywhere," U.S. Rep. Alan Grayson told reporters. "There's an enormous amount of evidence to be collected." Orlando Mayor Buddy Dyer said he had declared a state of emergency for the city and has requested the governor do the same for the state. Before Sunday, the deadliest shootings in U.S. history were at Virginia Tech in 2007 and Sandy Hook Elementary School in 2012, with 32 and 27 killed.