People hid under clothing racks as the giant baseball-sized hail broke through skylights and bombarded the shop floor of the store in the city of Norman.
It was part of a system of three hail storms that pummelled parts of Texas and Oklahoma and left a wake of damage in their path that could top $1bn.
Across the two states the National Weather Service received nearly three dozen reports of significant hail, of two inches or greater in diameter, and seventeen of baseball size or larger.
“Incredible vehicle damage in Norman. Talked with a Walmart employee who showed me a video of all 200 skylights breaking and hail falling into the store. The skylights are TWO layers of plexiglass,” wrote University of Oklahoma meteorology student Andrew Justin on Twitter.
Car dealerships in the city also saw windows of vehicles smashed by the hail storm.
“The total damage and economic loss caused by Wednesday night’s hail storms are predicted to be about $3.5 billion,” AccuWeather report, senior vice president and chief meteorologist Jonathan Porter said of the storms.