The burned Doctors Without Borders hospital is seen after the complex in the northern Afghan city of Kunduz was bombed on Oct. 3. (Médecins Sans Frontières via AP)

In the days since a U.S. gunship opened fire on a Doctor Without Borders hospital in Kunduz, Afghanistan, the Pentagon has struggled to explain how 22 people, including patients, staff and three children, wound up killed in the airstrike.

Officials have offered murky and contradictory statements on the incident, which Doctors Without Borders has called a war crime. Meanwhile, the top U.S. general in Afghanistan, Army Gen. John Campbell has pledged a full investigation into the attack, and the White House has expressed its condolences.

Below, a timeline of the Defense Department’s evolving account of what happened.

Saturday, Oct. 3

U.S. forces conducted an airstrike in Kunduz city at 2:15am (local), Oct. 3, against individuals threatening the force.  The strike may have resulted in collateral damage to a nearby medical facility.  This incident is under investigation.

—U.S. Army Col. Brian Tribus, a spokesman for U.S. forces in Afghanistan

Initial reports were extremely murky, with the Pentagon still not sure if it could confirm that a U.S. airstrike in fact had hit the hospital. The use of the military term “collateral damage” immediately inflamed the situation as Doctors Without Borders saw the classification of the strike as a dismissal of the incident. Under the Law of Armed Conflict, collateral damage is legal as long “as it is not excessive in light of the overall military advantage anticipated from the attack.”

Sunday, Oct. 4:

I think our current understanding, again, understanding that an investigation is going on and early facts can be misleading, is that yes, there was American air action in that area, and that American forces there were engaged in the general vicinity.

And at some point in the course of the events there did report that they, themselves, were coming under attack.  That much I think we can safely say.

—Secretary of Defense Ashton B. Carter to reporters while enroute to Spain

The day after the attack, with criticism mounting, Carter insisted that U.S. forces were essentially acting in self-defense. The Pentagon would only say that the attack was conducted “in the vicinity” of a Doctors Without Borders medical facility.

Monday, Oct. 5

We have now learned that on October, 3rd, Afghan forces advised that they were taking fire from enemy positions and asked for air support from U.S. Forces. An air strike was then called to eliminate the Taliban threat and several civilians were accidentally struck.

—Commander of U.S. forces in Afghanistan, Army Gen. John Campbell to reporters

Campbell appeared to be pointing the finger at Afghan forces for requesting the airstrike, and he said specifically that he was correcting earlier reports that indicated U.S. forces were directly engaged with the enemy when they called in the airstrike. Doctors Without Borders immediately responded to Campbell’s comment. “The reality is the U.S. dropped those bombs,” Christopher Stokes, general director of Doctors Without Borders, said in a statement. “With such constant discrepancies in the U.S. and Afghan accounts of what happened, the need for a full transparent independent investigation is ever more critical.”

Tuesday, Oct. 6:

Army General John Campbell clarified that the decision to provide air support to Afghan forces in Kunduz, which hit a hospital, was a U.S. decision. "We would never intentionally target a protected medical facility," Gen. Campbell said while testifying before the Senate Armed Services Committee on Oct. 6. (Associated Press)

A hospital was mistakenly struck. We would never intentionally target a protected medical facility.

—Gen. Campbell in testimony to Senate Armed Service Committee

…the Department of Defense deeply regrets the loss of innocent lives that resulted from this tragic event. The investigation into how this could have happened is continuing, and we are fully supporting NATO and Afghanistan’s concurrent investigations. We will complete our investigation as soon as possible and provide the facts as they become available.  The U.S. military takes the greatest care in our operations to prevent the loss of innocent life, and when we make mistakes, we own up to them.

—Defense Secretary Ash Carter in a statement

Four days after the attack, Carter and Campbell shifted their tone, saying the U.S. military was squarely responsible for the attack and those that needed to be held responsible would be.

Read more:

Afghan response to hospital bombing is muted, even sympathetic

The bloody history of Kunduz, from Afghanistan’s ‘Convoy of Death’ to now

In Kunduz, echoes of a 1988 guerrilla assault after the Soviets withdrew