To me that exercise should be the training, not the test. Its about training, you can't function well in any situation just by shooting a airsoft gun or playing a video game. If they practice that situation, train people what to do, they will preform good enough to save lives..
If they ran the same drill two more times, the effectiveness of the guy with the gun would improve each time.. thats why you train.
I do think you should probably be required to take some gun safety and training on guns before you are allowed to purchase one, after you pass a background check.
Training on how to keep your guns out of careless hands should be included.
I own lots of guns, I have also been shot. I do not think banning them would solve anything. Sorry Im getting off track, back to training, as with anything it take proper training to be good or effective at almost anything.
I dont think there is any one thing that can be done to prevent the type of thing that happened last week, I think there will need to be quite a few efforts made in several areas..IMO..