New York (CNN) -- A shooting at the Empire State Building -- one of the most iconic tourist destinations in New York City -- killed two people and wounded at least eight others Friday, a law enforcement official said.The shooter was one of the two killed, investigators said.A security guard chased the gunman down 5th Avenue and helped alert police, who shot the man at least three times, witnesses said.The man had opened fire with a large gun, they said."It's just a crazy scene here," said Rebecca Fox, who works across the street. She said she had been getting coffee with her headphones on when she saw people running.Fox said she saw a woman who had been shot near a brewery, as well as blood splattered on the sidewalk.One witness -- 22-year-old Max Kaplan -- said he heard at least nine shots and saw ambulances race to the scene."We're all very shaken up at the office," he said.Aaron Herman, a CNN iReporter, painted a portrait of confusion."It was a little chaotic, police had barricaded the area and I saw one woman who was a victim, I think she had been grazed," he said. "Some said they heard around three 'pops' and ran into nearby local stores to be safe."The White House said top aides told President Barack Obama about the shooting around 9:30 a.m. The shooting does not appear to be linked to terrorism, authorities said.Local and federal authorities who converged on the building around 9 a.m. closed several streets around 5th Avenue and 34th Street, snarling traffic in the heart of Manhattan.The Empire State Building is one of the most famous skyscrapers in the world and one of New York City's best-known tourist attractions.Each year, about 4 million people visit the building's two observation decks. At more than 1,453 feet tall, the landmark building reaches more than a quarter-mile into the sky.The area typically has a large security presence."There's always a focus and concentration on the building," said retired police officer Lou Palumbo"That building gets special attention."