I did some research on this, it's confusing since he's called a school resource officer sometimes, but that doesn't seem to be his actual title.
Long and short, I'm pretty sure he did have a loaded weapon and froze.
How someone could have that job for 32 years and it never occurred to him that he didn't have the instinct to take action when faced with calamity is unanswerable.
Every profession has a bell curve for competency, unfortunately for these kids this guy was way to the Left.