This news story from LV makes it sound like the confrontation between Wilcox and the nut jobs took place inside the store. IDK if he announced his presence or not but sounds like he never stood a chance because he didn't notice the second shooter.
http://www.8newsnow.com/story/25728824/coroner-identifies-man-killed-at-wal-mart
http://www.8newsnow.com/story/25728824/coroner-identifies-man-killed-at-wal-mart