#3 Somebodyelse: "If Grandma had her gun this wouldn't have happened."
It's called "weapons retention", meaning unless the gun is locked up, the owner needs to maintain control of the weapon.
"At least, that's what the NRA will probably tell us."
Of course, a 3-year-old is too young for proper firearms training, IMHO, but here's what the NRA's Eddie Eagle program actually teaches kids (notice #2 especially):
1 Stop! - This first step is crucial. Stopping first allows your child the time he or she needs to remember the rest of the safety instructions.
2 Don't touch! - A firearm that is not touched or disturbed is unlikely to fire and otherwise endanger your child or other people.
3 Run away! - This removes the temptation to touch the firearm as well as the danger that another person may negligently cause it to fire.
4 Tell a grown-up! - Children should seek a trustworthy adult, neighbor, relative or teacher if a parent or guardian is not available.