Shoppers stepped over the man on the ground and streamed into the store. When told to leave, they complained that they had been in line since Thursday morning.
Nassau police said about 2,000 people were gathered outside the store doors at the mall about 20 miles east of Manhattan. The impatient crowd knocked the man, identified by police as Jdimytai Damour of Queens, to the ground as he opened the doors, leaving a metal portion of the frame crumpled like an accordion.
"This crowd was out of control," said Nassau police spokesman Lt. Michael Fleming. He described the scene as "utter chaos."
Dozens of store employees trying to fight their way out to help Damour were also getting trampled by the crowd, Fleming said.
Items on sale at the store included a Samsung 50-inch Plasma HDTV for $798, a Bissel Compact Upright Vacuum for $28, a Samsung 10.2 megapixel digital camera for $69 and DVDs such as "The Incredible Hulk" for $9.
Damour, 34, was taken to a hospital, where he was pronounced dead about 6 a.m., police said. The exact cause of death has not been determined.
A 28-year-old pregnant woman was taken to a hospital, where she and the baby were reported to be OK, said police Sgt. Anthony Repalone.
Police said criminal charges were possible in the case, but Fleming said it would be difficult to identify individual shoppers. Authorities were reviewing surveillance video.
Wal-Mart Stores Inc., based in Bentonville, Ark., called the incident a "tragic situation" and said the employee came from a temporary agency and was doing maintenance work at the store.