According to the news story, two men got out of a pickup at 4:00 AM with guns and approached the guard, who shot and killed one of them.
According to the same story, the other man got back in the truck, left his friend behind, and drove away. It is not known whether he also got shot.
The fact that the other man chose to remain at large rather than calling the police or an ambulance for his partner tells me that these two guys weren't out at 4:00AM innocently exercising their Second Amendment right to open carry.