It took more than five hours to identify the suspect.
http://www.denverpost.com/2017/11/02/shoppers-pulled-weapons-walmart-shooting/

 “That’s when we started noticing” that a number of individuals had pulled weapons. “At that point, as soon as you see that, that’s the one you try to trace through the store, only to maybe find out that’s not him, and we’re back to ground zero again, starting to look again. That’s what led to the extended time.”