Sane people are not mass murders. Sane people kill for emotional reasons or for vengeance and frequently with no prior planning. They use various weapons, knives, drugs, guns, etc. Frequently, it is whatever is at hand like something heavy or sharp or even a car. I always loved the scene in "Fried Green Tomatoes" where the older women freaks out and bashes her car repeatedly into the car the young chippies just exited while shouting out that they may be young and fast (they snuck in front of her to take the parking place she had been waiting patiently for.), but she was older and had better insurance. Was the woman crazy as she was destroying their car?
If you were to examine the mental health of mass murders (almost always men BTW), you would find them to have some mental health problem. Many of them gave warning signs of impending action. Therefore many mass murder events could have been prevented but we are too politically correct to handle the problem. Even when dangerous behavior is reported to the police and FBI and coorabated, they don't/can't do anything because they would be accused of violating the "rights" of the dangerous person. I guess it is better to just let the crazy person go out and kill.
In the US, we've always had guns and in the past, we had more guns. Did we have mass murders in the past? I don't know but I'm pretty sure they are a product of the 20th century.
We emptied our mental hospitals in the 80's and let all those people out to become homeless because it just wasn't "fair" to keep them in mental hospitals. Of course, without supervision, they didn't take their meds and their conditions worsened to the point where many became dangerous. This precipitated the homelessness crisis we face today.
And now all of our children seem to have some "condition" that requires drugs. How many of the younger mass-murderers were on prescription drugs for hyperactivity, depression, autism, etc? How many had been victims of bullies that the schools never reprimanded or stopped from injuring other children because the parents would have sued the school if it had taken action. How many had been victims of abuse or neglect at home? Can we at least talk about this instead of running off and passing new gun laws that won't do anything to solve the problem?