Judging from the fact that he only fired 6 shots and his slide didn't lock back, I would guess that his gun WASN'T unloaded.
Much more than a guess - I would bet the rent on it.
Checking around you for second assailants (or more) is widely taught, if not universally. The alternative is to be oblivious of other threats. Do you have to do it at the range? Well, no, but the range is where you develop habits.