A year ago, when a gunman opened fire at the Fort Lauderdale airport with a 9 mm semiautomatic handgun, hitting 11 people in 90 seconds, I was also on call. It was not until I had diagnosed the third of the six victims who were transported to the trauma center that I realized something out of the ordinary must have happened. The gunshot wounds were the same low-velocity handgun injuries that I diagnose every day; only their rapid succession set them apart. And all six of the victims who arrived at the hospital that day survived.

Routine handgun injuries leave entry and exit wounds and linear tracks through the victim’s body that are roughly the size of the bullet. If the bullet does not directly hit something crucial like the heart or the aorta, and the victim does not bleed to death before being transported to our care at the trauma center, chances are that we can save him. The bullets fired by an AR-15 are different: They travel at a higher velocity and are far more lethal than routine bullets fired from a handgun. The damage they cause is a function of the energy they impart as they pass through the body. A typical AR-15 bullet leaves the barrel traveling almost three times faster than—and imparting more than three times the energy of—a typical 9mm bullet from a handgun. An AR-15 rifle outfitted with a magazine with 50 rounds allows many more lethal bullets to be delivered quickly without reloading.

I have seen a handful of AR-15 injuries in my career. Years ago I saw one from a man shot in the back by a SWAT team. The injury along the path of the bullet from an AR-15 is vastly different from a low-velocity handgun injury. The bullet from an AR-15 passes through the body like a cigarette boat traveling at maximum speed through a tiny canal. The tissue next to the bullet is elastic—moving away from the bullet like waves of water displaced by the boat—and then returns and settles back. This process is called cavitation; it leaves the displaced tissue damaged or killed. The high-velocity bullet causes a swath of tissue damage that extends several inches from its path. It does not have to actually hit an artery to damage it and cause catastrophic bleeding. Exit wounds can be the size of an orange.

With an AR-15, the shooter does not have to be particularly accurate. The victim does not have to be unlucky. If a victim takes a direct hit to the liver from an AR-15, the damage is far graver than that of a simple handgun-shot injury. Handgun injuries to the liver are generally survivable unless the bullet hits the main blood supply to the liver. An AR-15 bullet wound to the middle of the liver would cause so much bleeding that the patient would likely never make it to the trauma center to receive our care.

One of my ER colleagues was waiting nervously for his own children outside the school. While the shooting was still in progress, the first responders were gathering up victims whenever they could and carrying them outside the building. Even as a physician trained in trauma situations, there was nothing he could do at the scene to help save the victims who had been shot with the AR-15. Most of them died on the spot; they had no fighting chance at life.