When the robber pulled out his gun he quickly discovered that Alexander — an Iraq War veteran with four tours of duty and 30 years of service in the U.S. military — had a firearm of his own.
(Alexander was also former prison guard, private investigator, and professional extraditor of federal prisoners, so basically, not a guy you want to try and rob.)
The surveillance footage shows the robber demanding that Alexander give him all the money in his register — that is until Alexander smoothly pulls a Walther PPX 9 mm handgun.