This is a slightly horrifying account from a Florida radiologist, whose presence as an Atlantic writer is explained by the fact she's attacking gun rights.

What I Saw Treating the Victims From Parkland Should Change the Debate on Guns
They weren’t the first victims of a mass shooting the Florida radiologist had seen—but their wounds were radically different.
By Heather Sher, The Atlantic, Feb 22, 2018 Text Size

As I opened the CT scan last week to read the next case, I was baffled. The history simply read “gunshot wound.” I have been a radiologist in one of the busiest trauma centers in the nation for 13 years, and have diagnosed thousands of handgun injuries to the brain, lung, liver, spleen, bowel, and other vital organs. I thought that I knew all that I needed to know about gunshot wounds, but the specific pattern of injury on my computer screen was one that I had seen only once before.

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. [More]

What this means is that murders committed with high-powered rifles are so vanishingly rare that she had only seen it once before. Even the Huffington Post admits this: Thousands Of Americans Are Gunned Down Each Year, But Few Die By Assault-Style Rifle, By Nick Wing, June 17, 2016.

See that flattish orange line at the bottom? Rifle homicides:

From The Trace, via The Truth About Guns.

The AR-15 is considered under-powered by many gun enthusiasts.  The bullet it fires is faster but smaller than the one fired by any ordinary deer rifle, which would wreak the same damage—it certainly does when you shoot a deer.

This urge to ban rifles is a typical of the twists and turns of gun control—for years, they've been saying "We're not after your deer rifles, we just want to ban concealable handguns" and now they're saying the opposite.

In 2013,  I made a speech titled Gun Control—Like Immigration Law, Enforced Only Against Those Who Obey It,  I discussed the Minuteman Movement, whose members carried, but did not fire, rifles like the one used by Cruz in Florida:

The Minuteman Movement’s tactics were based on the principle of guarding the border, but not engaging the illegals directly, only observing and reporting. Nevertheless, they all carried guns. Without guns, their mission would have been suicidal, since the illegals are frequently dangerous criminals, and travel in large groups. 

The rifle of choice for Americans engaged in duties like patrolling the border is the semi-automatic AR-15. Old school gun experts are still, after 50 years, unhappy with the .223 cartridge. But the cartridge works most of the time, the gun always works, and it’s the rifle millions of American veterans are trained in using.

It’s the latest target of a ban, because it was used in a recent crime at Newtown. The question is always “Why would anyone need that many bullets?”

The answer is there are a lot of rioters in a mob, whether the old style of lynch mob or the newer style of race riot, and illegals, when marching across the border, come in groups of mob size. A Georgia woman (white) recently emptied her six-shot gun into an attacker (black), and didn’t  kill him. (But he did desist).[M.D. Harmon: Tale of two terrorized women shows value of being armed, Portland Press-Herald, January 11, 2013]

In March, 2017 , a young man in Oklahoma woke up and found three masked, armed,  home invaders in his family's house. He defended himself with the rifle at right, and the attackers were all "Dead Right There"—no doubt the local coroner saw the same kind of thing that radiologist Heather Sher saw above.

The police said it was a clear-cut case of self-defense, and laid no charges.  If he'd had a pistol, one of them might have lived long enough to kill him.