Why did the US launch an airstrike on a hospital run by Doctors Without Borders in Afghanistan, killing 22 people, including three children?

The Pentagon has changed its story and now calls the attack a mistake. The Justice Department is investigating. And Doctors Without Borders says the incident may constitute a war crime, an assertion that rankles some experts and has provoked a spirited discussion on Reddit.

“Under the rules of international humanitarian law, a hospital is a hospital and the people inside are patients — to target a medical facility in this way is a violation of that, whatever the circumstances,” Vickie Hawkins, executive director of the UK branch of Doctors Without Borders, tells The Takeaway. “The statements that have been coming out of the Afghan government in the past 24 hours would lead us to believe that there was some kind of intent behind the attack. We can only presume, on this basis, that that constitutes a war crime.”

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On Wednesday, the group urged a probe by the International Humanitarian Fact-Finding Commission, created by the Geneva Conventions. “It is unacceptable that the bombing of a hospital and the killing of staff and patients can be dismissed as collateral damage or brushed aside as a mistake,” the group's international president, Joanne Liu, said. “This was not just an attack on our hospital. It was an attack on the Geneva Conventions. This cannot be tolerated.”

The US says the strike in Kunduz, which is under investigation, was issued after Afghan forces came under fire near the hospital and then called for help. Nonetheless, hitting the hospital was a mistake, the American commander in Afghanistan, Gen. John F. Campbell said. "We would never intentionally target a protected medical facility," Campbell said.

The general said that he was not in a position to provide more details about what happened, including who may have failed to follow military guidelines to avert attacks on hospitals, according to the BBC.

The White House on Tuesday announced that Department of Justice would investigate the air strike.

During a press briefing on Monday, Campbell acknowledged he was taking a different tack from initial statements, "which indicated that US forces were threatened and that the airstrike was called on their behalf.”

Though the aid group repeatedly said that there had been no fighting around the hospital, the building was hit over and over again, despite the fact that Doctors Without Borders sent the US military the precise GPS coordinates so the hospital could be avoided.

“When the bombing started, we were indeed in contact with military representatives in both Kabul and in Washington, but the bombing continued for another half hour to 40 minutes after those initial calls were made,” says Hawkins.

The hospital is the only facility of its kind in the northeast region of Afghanistan, and Hawkins says the compound where it sits was “precisely targeted,” adding that the intensive care unit and the emergency room were hit the worst. For four years, Doctors Without Borders has been using this facility to provide free high level trauma care to civilians in the area.

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“For our medical staff, it was an absolutely terrifying experience,” says Hawkins. “The hospital itself had been very busy over the previous days [before the airstrike] — there’s been an uptick in the conflict around Kunduz, and we’ve had 400 patients over the last four days or so.”

According to Doctors Without Borders, more than 22,000 patients received care at the hospital in 2014, and more than 5,900 surgeries were performed during the same time period. When the hospital was hit, medical workers were in midsts of caring for patients.

“After the attack was over, we found one of our patients that was killed still on the operating table,” says Hawkins. “You can imagine for the medical staff that’s going about their night’s work, this is an absolutely a devastating experience for them.”

The group is now planning to leave the area, something that could be devastating to civilians in the area — Hawkins describes the trauma center as a “vital lifeline” for the community.

“A hospital should represent a place of sanctuary — it’s where people come when they’re at their most vulnerable,” she says. “Given the fact that the intensive care unit was targeted, we can presume that the most sick and vulnerable of our patients have been killed.”

But a war crime?

“I don’t think we know yet,” says Charlie Dunlap, a former Deputy Judge Advocate General for the US Air Force. He’s now a professor and director of the Center for Law, Ethics and National Security at Duke University’s Law School. He says even in war time there should be a presumption of innocence until proven guilty.

“What surprises me,” says Dunlap, “about what Doctors Without Borders is saying — an organization I previously had a lot of respect for — is they’re making conclusions before the facts have even been gathered.”

“In war zones there’s a lot of complexity about the application of force,” adds Dunlap, “and (about) what’s going on on the ground. We’ve all heard about the chaos, and fog and friction of war. And that’s what’s going on.”

“We need to assemble the facts before we start making very, very serious accusations against people.”

Doctors Without Borders says there were repeated attacks, about every 15 minutes, over the course of more than an hour. Neighboring buildings were unharmed. “That would seem to indicate that they were deliberately targeting that building,” says Dunlap. “But I don’t know if that means they’re deliberately targeting because it was a hospital.”

“International law does not prohibit conducting an attack, even when you know for an actual fact that civilian casualties will occur. What international law only prohibits is that they not be excessive in relation to the military advantage anticipated. And that’s to preclude incentivizing parties to actually use civilians as human shields. Unfortunately though we’ve seen adversaries who nevertheless do it, and I think that is really one of the complications of 21st century warfare.”

“One of the things we need to look at, is of course whether it (the hospital) was being used in any way by the Taliban as a military position to shoot or launch attacks against Afghan and other allied forces.”

“Then we also have to explore whether a mistake was made,” says Dunlap. “In other words, it’s not a war crime if people are acting reasonably and doing the best they can in what we would all agree would be a very chaotic and difficult situation, and something you don’t want to happen, happens.”

“If a hospital is being used for military purposes, it can become a target. You still have to do a proportionality analysis. In other words, you have to make a determination that the anticipated military advantage you’re going to gain will not cost excessive civilian casualties.”

This report was based upon an interview on PRI's The Takeaway, a public radio program that invites you to be part of the American conversation. T.J Raphel is a digital producer for The Takeaway. Christopher Woolf is a producer for PRI's The World. Listen to host Marco Werman's interview with Charlie Dunlap, former Deputy Judge Advocate General for the US Air Force here.