(Adds fresh Wal-Mart comment and union statement) NEW YORK, Nov 28 (Reuters) - A man working for discount retailer Wal-Mart <WMT.N> was killed on Friday in a stampede by frenzied shoppers who broke down doors and surged into a Long Island, New York store, a police spokesman said. The 34-year-old man was at the entrance of the Valley Stream Wal-Mart store just after it opened at 5 a.m. and was knocked to the ground, the police report said. The exact cause of death was still to be determined by a medical examiner. Four shoppers, including a 28-year-old pregnant woman, were also taken to local hospitals for injuries sustained in the incident, police said. Wal-Mart said it was saddened by the death of the man, who was working for a temporary employment agency serving the retailer, and by the injuries suffered by shoppers. "The safety and security of our customers and associates is our top priority," the world's largest retailer said in a statement. It said the incident was still under investigation and referred any other inquiries to local police. New York's largest grocery workers union on Friday urged federal, state and local authorities to investigate what it called "Wal-Mart's failure to provide a safe workplace." "This incident was avoidable," said Bruce Both, president of United Food and Commercial Workers Union Local 1500. "Where were the safety barriers? Where was security? ... This is not just tragic; it rises to a level of blatant irresponsibility by Wal-Mart." Wal-Mart said it had added additional internal security, third party security, more store associates and had worked closely with local police. "We also erected barricades. Despite all of our precautions, this unfortunate event occurred," Hank Mullany, a Wal-Mart senior vice president, said in a statement. The Friday after America's Thanksgiving holiday is known as Black Friday and is traditionally the busiest retail day of the year, kicking off the Christmas shopping season. U.S. stores across the country opened early to offer discounts to consumers hit by a contracting economy. Hundreds of shoppers waited in line before dawn at some locations to secure deals on holiday gifts. (Additional reporting by Andrea Shalal-Esa in Washington) (Reporting by Michele Gershberg; Editing by Daniel Trotta and Anthony Boadle)
