A 53-year-old fashion accessories designer, disgruntled over being fired a year ago, shot and killed a 41-year-old former co-worker three times with a .45 caliber handgun on a sidewalk near the landmark building, officials said.

Police returned fire, killing the shooter and wounding several bystanders, all of whom were expected to survive, Mayor Michael Bloomberg told a news conference.

Police Commissioner Raymond Kelly identified the shooter as Jeffrey Johnson of Manhattan, who had worked at Hazan Imports across the street from the skyscraper. The shooting took place outdoors, at the height of the tourist season by one of New York City's most popular attractions

A white tarp covered Johnson's body in front of the entrance to the office building. There was no link to the historic tower - it just happened to be next door - and Bloomberg ruled out any connection to terrorism.

"I heard the gunshots. It was like pop, pop, pop. It was definitely in a bunch," said Dahlia Anister, 33, who works at an office near the 102-story building.

It was the third mass shooting of the summer in the United States, following an assault on a crowded cinema in Colorado and an attack on a Sikh temple in Wisconsin, rekindling debate about gun control in America.

"We are not immune to the national problem of gun violence," said Bloomberg, a leading national proponent of gun control and founder of the group Mayors Against Illegal Guns. (Additional reporting by Mark Hosenball and Chris Francescani; Writing by Daniel Trotta; Editing by Vicki Allen)

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