Add to that list:
Knife attacks by estranged spouses that was stopped by a gun carrying customer.
Suicide (in my local WalMart). A customer walked up to a greeter, said hi, pulled a gun and shot himself. He didn't even know her.
For those who think that 5 five is close enough to reach, I guess they've never seen a 3 year old take off running when you call them. That 5 feet can quickly be ten feet and out of sight.
In todays world, parents must be extra vigilant. Back in the day, you could count on other adults in the store (or park, wherever) to alert you or help the child.
Today you better NOT count on any adult stranger or any teenage stranger even NEAR your child. No one will help you and your child but yourself.