The difference is that "opened fire" is a weasel word in this instance- it is misleading as it linguistically leaves open the interpretation that multiple people were injured or killed
Until I read cwkoss' comment right now I had always assumed someone came to the pizza joint and started firing rounds at people. I admit I'm not American so I never cared enough to look up what "opened fire" meant here, but I think it's evident what people will think of when they read that expression. Hint: not someone shooting a closet's lock once to open it.
It was multiple shots, and he pointed the gun at employees first. See my other comment for references.