(CNN) -- The tourists were lined up outside the door. The observation tower was open. Just another early morning at the Empire State Building, one of New York's most-visited attractions.
Even the frenzy of people running down the street seemed routine enough, given the building's popularity.
"I thought actually there was a celebrity sighting," said Rebecca Fox, who saw a surging crowd while she was on her way for coffee.
The crowd wasn't running to see a star. They were running from a shooting.
A man opened fire outside the building's Fifth Avenue entrance, triggering a gun battle with police, authorities said. At least 10 people were shot and two of them were killed, including the gunman.
At mid-morning, the man's body lay on the pavement, just feet from the entrance to the building's observatory. A black bag lay next to him. Detectives swarmed over the scene.
Nearby, Fox saw a woman who had been injured, the sidewalk stained with blood.
"I could see the obvious shock on her face," she said. "It's just a crazy scene."
CNN iReporter Ashwin Purushan stumbled across the scene on his way to work.
"There was a sense of panic and mass confusion," he said.
Police closed down the streets near the Empire State Building, which attracts 3.6 million visitors a year. Onlookers crowded up to police barricades, chattering about the shooting, CNN iReporter Kelly Wilson said.
Another iReporter, Vladimir Dusio, who lives across the street from the building, said his normally busy block looked very different after the shooting.
"I don't see any pedestrians around our building at all, I just see cops," Dusio said.
Wilson, who took a photo of the aftermath of the shooting, told CNN he had realized what was going on from the murmuring of the crowd. He hustled on as swiftly as possible to get to work and away from the scene.
"It's a terrible thing. The first impulse is to think about whether it's time to get out of the city," he said. "That was an immediate thought, then my next thought was even if I left the city, I'd still be coming to work in the city so there's no way to avoid it."
Wilson said the recent spate of shootings seemed to suggest that "some people are getting less sensitive to the value of other human lives."
While authorities say the shooting was not related to terrorism, the fear of such violence wasn't far from the minds of some people who live and work nearby, witnesses said.
For some, the shootings dredged up memories of the September 11, 2001, terrorist attack that toppled the twin towers of the World Trade Center and left the Empire State Building as New York's tallest building.
"For us, it's one of the worst nightmares, to be subjected to something like this. And because the Empire State Building is such an iconic building and there is so much traffic there, you always wonder if someone is going to do something there," Dusio said. "It is very unsettling."
CNN's Rose Arce, Anika Chin and Jareen Imam contributed to this report.