The robber’s gun was fake and painted, but that’s impossible to tell in the moment and realistically, doesn’t matter one bit. A threat is a threat and if a robber wants to play serious games with a fake firearm, they need to be prepared for the consequences.
The armed robber walks into the store and pulls out a fake desert eagle and points it at the store owner and a customer. As the robber is trying to figure out what to do next, the store owner changes his position to allow a nice draw of his firearm from concealment. He then fires multiple shots at the armed robber, sending him fleeing but not getting too far from the crime scene.
Had this robber used a real and working firearm, the store owner may not have had the same outcome.