An employee who was fired by his company shot dead a former co-worker outside New York's Empire State Building and then randomly opened fire on people nearby.
Nine people were wounded in the shooting, but mayor Michael Bloomberg said that some of the injured may have been hit by police bullets as they exchanged fire with the gunman.
The shooter, identified as Jeffrey Johnson, 58, was shot dead by police.
All of the wounded were expected to survive, Mr Bloomberg said.
Johnson had worked for six years as women's accessories designer at Hazan Imports, which is housed in the Empire State Building, but he was laid off about a year ago.
Police Commissioner Ray Kelly said Johnson fired at his former colleague three times at close range after a dispute about 9am. The name of the 41-year-old victim was not released.
Johnson then tried to flee but he was confronted by police who had been alerted by a nearby construction worker, Mr Bloomberg said.
"The perpetrator clearly turned his gun on the police and tried to shoot them," Mr Bloomberg said.
"The cops returned fire, killing him."
Authorities said they had little details about Johnson's background yet.
The FBI said it quickly ruled out terrorism.
The shooting caused chaos in the heart of Manhattan at the height of the summer travel season and just after the morning rush hour.
Police on their regular anti-terrorism duties in the tourist area rushed to the scene.
Aliyah Imam told Fox 5 News television she was standing at a red light when a woman next to her fell to the ground. She said the woman was hit in the hip.
The gunman was "shooting indiscriminately at people", Ms Imam said.
Witness Rebecca Fox said: "I was scared, in shock, literally shaking. It was just by chance I missed it.
"I saw a woman covered with blood. Another woman was being taken to an ambulance."
The Empire State Building is one of the city's icons, on par with the Statue of Liberty and the Brooklyn Bridge.
In 1997, six people were wounded and one killed in a shooting rampage on the skyscraper's observation deck before the gunman turned the gun on himself.