Discretion is the better part of valor. Given their training and pay, I expect cops to attempt to maintain order and deescalate volatile human conflicts–especially in the case of school resource officers, whose daily routine might get as exciting as breaking up a fistfight. I don’t particularly want that guy to be armed in the first place, and I especially don’t want him to be eager to draw his weapon and go a-hunting through the high school full of scared and flighty kids.
With Parkland in particular, my criticism is limited to allowing the shooter access to the school. I’m not clear about how that happened without a cop being made dead at the point of entry. But once someone breaks out the big guns, it’s SWAT time. A resource cop with his little pea shooter is just another casualty. If he gets a clear shot that doesn’t threaten innocents, then I expect him to take that shot. But going on a hunt when that’s not something he’s well trained to do is to court disaster.