Witnesses to the early morning incident in Valley Stream, N.Y., said the unidentified worker had been attempting to hold back a wave of customers after the store opened, only to be knocked down and trampled underfoot, the New York Daily News said.
"He was bum-rushed by 200 people," Jimmy Overby, a co-worker of the man's, said. "They took the doors off the hinges. He was trampled and killed in front of me. They took me down too ... I literally had to fight people off my back."
Police said the incident was being investigated and the body would be analyzed to determine the official cause of death.
Meanwhile, shopper Jessica Keyes said she miscarried after being knocked down by her fellow shoppers at the same Wal-Mart.
She told the Daily News that paramedics informed her she had lost her unborn child from the violent collision.
"There's nothing we can do. The baby is gone," she quoted the paramedics as saying.