The Parkland, Florida, massacre that claimed the lives of 17 wasn’t Heather Sher's first time dealing with gunshot wounds, but it was hardly business as usual.

Sher, a radiologist in one of the country’s busiest trauma centers for 13 years, wrote in The Atlantic that she diagnoses a typical handgun injury just about every day. She uses imaging to track bullets in a patient’s body, as they slice through vital organs, leaving blood and bullet fragments in their wake. The process, though violent in reality, appears as a simple, gray line on a CT scan.

In addition to treating those involved in last week's high school shooting, Sher was on call when a gunman opened fire at the Fort Lauderdale airport last January, when six victims arrived at her facility with critical injuries. They all lived.

The reason the Parkland victims lacked that same chance at survival, she said, was the shooter’s weapon of choice.

The AR-15, a semi-automatic rifle, moves faster than a traditional 9mm handgun, she wrote, passing through the body “like a cigarette boat traveling at maximum speed through a tiny canal.” The high-velocity bullet is capable of destroying tissue and damaging arteries without even grazing them. Exit wounds, Sher said, can be the size of an orange.

“With an AR-15, the shooter does not have to be particularly accurate,” she wrote. “The victim does not have to be unlucky.”

Sher said much of the effort to save Parkland victims was fruitless because of this. Since an AR-15 is such a powerful weapon, “most of them died on the spot, with no fighting chance at life.”

“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,” she wrote. “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 an individual’s gun cabinet."

Read Sher’s full essay in The Atlantic: