The China stabbing has been and continues to be selectively used by the radical pro AND anti-gun lobby as "proof" of their position. Pro-gun radicals say it proves total gun bans do not prevent mass attacks; anti-gun radicals say it proves total gun bans prevent fatalities even when nutjobs attack kids. Rational people realize the total gun ban prevented a nutjob killing anyone, but also prevented a rational, law-abiding and trained gun user from preventing the ATTACK.

That COPS stop would-be mass shooters (and it is VERY telling how often cops, rather than random private citizens, do so) demonstrates that screened, trained and certified gun owners are no threat to anyone, and often a great benefit to everyone. It does not demonstrate that everyone—including convicts, the mentally ill and the untrained—should be able to get a gun. The inability to completely prevent the latter is a good argument for the former, but not for doing nothing to prevent the latter.