What An AR-15 Does
By 
A radiologist describes what she found examining victims Marjory Stoneman Douglas:
In a typical handgun injury that I diagnose almost daily, a bullet leaves a laceration through an organ like the liver. To a radiologist, it appears as a linear, thin, grey bullet track through the organ. There may be bleeding and some bullet fragments.
I was looking at a CT scan of one of the victims of the shooting at Marjory Stoneman Douglas High School, who had been brought to the trauma center during my call shift. The organ looked like an overripe melon smashed by a sledgehammer, with extensive bleeding. How could a gunshot wound have caused this much damage?
The reaction in the emergency room was the same. One of the trauma surgeons opened a young victim in the operating room, and found only shreds of the organ that had been hit by a bullet from an AR-15, a semi-automatic rifle which delivers a devastatingly lethal, high-velocity bullet to the victim. There was nothing left to repair, and utterly, devastatingly, nothing that could be done to fix the problem. The injury was fatal.
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As a doctor, I feel I have a duty to inform the public of what I have learned as I have observed these wounds and cared for these patients. It’s clear to me that AR-15 or other high-velocity weapons, especially when outfitted with a high-capacity magazine, have no place in a civilian’s gun cabinet. I have friends who own AR-15 rifles; they enjoy shooting them at target practice for sport, and fervently defend their right to own them. But I cannot accept that their right to enjoy their hobby supersedes my right to send my own children to school, to a movie theater, or to a concert and to know that they are safe. Can the answer really be to subject our school children to active shooter drills—to learn to hide under desks, turn off the lights, lock the door and be silent—instead of addressing the root cause of the problem and passing legislation to take AR-15-style weapons out of the hands of civilians?
Conservatives are going to try to divert the debate by proposing a whole bunch of counterproductive security theater. Liberals can’t play into that. The focus needs to be on gun control. Inter alia, civilians should not be able to own weapons like the AR-15. The cost-benefit analysis is not close, and such a ban does not raise a serious constitutional question.