One man was outside, near the front entrance, and the other was inside when the shooter opened fire about 2 p.m., shattering one of the glass doors at Best Buy, 5520 E Skelly Drive.
The man outside the store, Scott Norman, 34, of Tulsa, was shot eight times in the back. The shooter approached him on foot from between some cars in the parking lot, Tulsa police Sgt. Mike Williams said.
More than a dozen shots were fired, including one bullet that went through the sliding glass door and struck Graydon Brown, 58, of Tulsa, who was inside the store.
Brown and Norman were taken to St. Francis Hospital where they died. Police said the two men did not know each other.
The shooter is described as a black man who is 5 feet 8 inches tall and about150 pounds. He was wearing a white shirt with black print on it.
Anyone with information about the shooting is asked to call Crime Stoppers at (918) 596-2677.
The slayings are the 27th and 28th homicides in Tulsa this year, The Tulsa World reported.
Contributing: Amanda Bland, The Tulsa World