For other cases such as the Aurora shooting or shootings at malls, all it would do would be to give somebody that's going to do this more confidence that there won't be another person there with a gun.
Something has to change. I know that. But that something is not stricter gun control. that something is better security at schools. Armed guards or unarmed guards, escorting visitors, metal detectors... Better care for mentally unstable. Better education on the warning signs of violent intentions. More security at public locations. There are dozens of methods better suited for minimizing these types of attacks.
If it was up to me, I'd put a gun in the hands of every single person for stricter gun control. Why? Because the average number of deaths in a shooting rampage when stopped by police is 14.3 deaths. The average number of deaths in a shooting rampage when stopped by civilians is 2.3 deaths.
In cases when armed civilians put a stop to mass murderers, an average of twelve lives are saved.
The answer is not in gun control.