So there was a previous blog post showing pictures of a store not sure if it was a Wal-Mart, in the middle of filming for the Walking Dead. They are most likely filming Episode 1 or 2 of Season 4. But what role will it play, to be honest I can't see it being just the sight of a simple supply run by either side.
This is my opinion, Rick, and a few other group members enter the store looking for supplies bypassing the military equipment outside which looks like a simple truck and a tent. A few minutes after they enter, The Governor, Shumpert, and Martinez enter, neither group knows they are inside. Shumpert spots them first and opens fire, a gunfight ensues, and Rick's group escapes with Glenn, or someone with a gunshot wound.