Wal-Mart followed policy and evacuated the store but here is the rest of the story.
The man with a gun was a customer with a CCL who had just been assaulted by another customer for unspecified reasons - Investigators has charged Herbert Harris with assaulting James Heath at the electronic section at Wal-Mart. Heath pulled his gun in defense of himself. There was an off duty cop in the store that showed and arrested Harris for the assault. Heath was questioned and showed the cop his permit
There is video showing Mr. Heath pulling his gun and I have to say he had a smooth draw and was ready