Rockb, Again you are telling me US is the only country in the world who has mental health crisis,drug and bullying crisis. There are many many countries in the world who has far far worse countries in the world who has far more problem and severe problem than US. Dude, you are talking about one of the most developed countries in the world. You are still pointing to side problem not the actual problem. It's the abundance of Guns where it's extremely easy to get a gun. Also, regarding your idea of AR-15. Give me a reason why anyone needs a AR-15 beside fighting in battle field? How can you expect 8 billions people in this world living with right mind. Few of them will have mental health issues always. Ofcourse , we can't eliminate mass shooting 100% with any it greatly helps to reduce it.

Here is an example. If we don't have law of seatbelt, imagine how many people would die everyday. Your argument would say its people responsibility to drive the car carefully but they don't. Some people are careful, some are careful, some are evil etc.

I am not saying mental health is not an culprit but that's not the main culprit. Illegal guns will go away ultimately not in a day or two but years or decades but not unless people like Gary Abbott who advocates supply of gun. You have to start somewhere.
Those who are saying "Guns don't kill people, people kills people". Yes true but it makes 100x easier for people to people with guns.