Orlando, Florida (CNN)A gay nightclub here was the scene early Sunday of the worst terror attack in U.S. history since 9/11.

* 50 people were killed inside the Pulse club and at least 53 people were injured, police say.
* The gunman was Omar Mateen of Ft. Pierce, Florida, a law enforcement source told CNN.
* Orlando police shot and killed Mateen.
"It appears he was organized and well-prepared," Orlando Police Chief John Mina said early Sunday. The shooter had an assault-type weapon, a handgun and "some type of (other) device on him."
There has been no claim of responsibility for the attack on jihadi forums, but ISIS sympathizers have reacted by praising the attack on pro-Islamic State forums.
Officials, aided by the FBI, warned that a lengthy investigation was ahead, given the number of victims and the scope of the violence.
Follow
GLAAD ✔ @glaad
Our hearts break for the victims and families of this horrific act of violence. We stand in solidarity with the LGBTQ community in #Orlando.
8:51 PM - 12 Jun 2016
1,814 1,814 Retweets 1,506 1,506 likes
"There's blood everywhere," U.S. Rep. Alan Grayson told reporters. "There's an enormous amount of evidence to be collected."
It's just shocking," said Christopher Hansen, who was inside Pulse when he heard gunshots, "just one after another after another."
"It could have lasted a whole song," he said.
Hansen was getting a drink at the bar about 2 a.m. when he "just saw bodies going down."
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.