SCIENCE said:

what was exactly right about pointing the gun at the disarmed exshooter, and what was exactly right about letting them walk instead of restraining them

“what was exactly right about pointing the gun at the disarmed exshooter…”

It very readily communicated that ‘i have the gun now, don’t try to take it back, you may very well regret the attempt’.

“what was exactly right about letting them walk instead of restraining them”

The man on the spot made the decision. You or i might have made a different decision. Or we may have made the same decision as Ahmed. He’d taken the gun away from the shooter, he had eliminated that threat, he was not to know whether the shooter might subsequently have access to other guns, the man was backing away and not attacking him, Ahmed may have been aware that the other shooter was able to fire at him (he was subsequently hit twice) and thus didn’t want to pursue the man, and he may have had some moral qualms about shooting someone who was running away

He undoubtedly had a lot going through his mind, in a very stressful situation. It would be very presumptuous of us to criticise his decisions. We can suggest what we ourselves might have thought of doing, but we’re in no position to question what he did or didn’t do.