The story reported that the murderer was an off-duty security guard, a job which bestows the same authority to issue orders to citizens or kill them for noncompliance as does that of an off-duty pizza delivery guy.
The story also reports that it is unclear where he is employed as a guard. That's fair enough, since whether he is a guard or not doesn't matter. It does put him in a uniform, which I suppose means something to people who believe uniforms automatically grant killing authority.