I think the little children were huddled close together and terrified. Frozen.
I think you’re just wrong.
I doubt you're thinking. If they were huddled, then how did he hit the ones in the middle? How did he get KILL shots on almost EVERY person he targeted, when most similar massacres did NOT end that way? If he had the .223 that he left in the car, I'd give him better odds of beating a 1-to-1 kill ratio... but he had handguns, terrified targets, screaming, knew the cops were going to be there soon, adults as well as kids at target, had to reload at least ten times (for 100 shots), and as you say, kids could have been huddled... and he topped a ONE-TO-NINE ratio
The kill ratio IS worth looking into. It is out of whack with the usual results of these kinds of incidents. Beslan (elementary school hostage-taking) had 1100 victims, but "only" 380 killed. Columbine was 21-to-13. China's knife-attack had 22 injured, ZERO dead (and they were also tiny, frozen, fragile grade-schoolers).