KABUL, Afghanistan >> The Doctors Without Borders hospital was among the most brightly lit buildings in Kunduz on the night a circling U.S. gunship destroyed it.

The rest of the northern Afghan city was mostly dark after days of fighting between the security forces and Taliban militants. But the hospital was keeping its lights on as doctors there were working, according to the group’s general director, Christopher Stokes.

Spread across the hospital roof was a large white and red flag reading "Medecins Sans Frontieres," the group’s French name. On the afternoon before the strike, the fighting in the neighborhood had quieted enough for staff members to safely climb to the roof and lay out the markers identifying the building to any military aircraft flying over.

The group had also sent the longitude and latitude coordinates of the hospital, for years the most important trauma center in that part of northern Afghanistan, to the U.S. military to remind it where not to attack during the fighting.

Despite all that, and the protection afforded to war-zone hospitals by the Geneva Conventions, the hospital was gutted by a U.S. bombardment in the early hours of Oct. 3. The strikes occurred over an hour and 15 minutes and killed 30 people, including patients on operating tables and the wounded in their beds and wheelchairs.

At a news conference in Kabul on Thursday, the international medical organization said that more than a month after the attack the U.S. military had yet to offer an explanation for why a clearly marked hospital was struck, other than to say it had been hit by mistake.

"A mistake is quite hard to understand and believe at this stage," Stokes said at the news conference. The organization shared more details of the attack and renewed its call for an independent investigation, which both the United States and Afghanistan have resisted so far. "From what we are seeing now, this action is illegal in the laws of war. You cannot do this. You cannot bomb a hospital."

As details continue to emerge that suggest that the military struck the target it intended to hit that day, a troubling question hangs over the various investigations into the attack: Did someone intentionally decide to fire on the hospital, whether because of the presence of wounded Taliban fighters there or for some other reason?

As Stokes put it, "Did our hospital lose its protected status in the eyes of the military forces engaged in this attack, and if so, why?"

The main hospital building, the most clearly marked in the medical complex, received the brunt of the bombardment on Oct. 3. The perimeter of the hospital was mostly spared, suggesting that the main hospital building was the specific target of the various aerial passes by the U.S. Special Operations AC-130, a gunship used by the military because of its ability to deliver precise strikes on one spot over an extended period of time.

So far, the U.S. military has offered few details to explain how the strikes happened.

After the airstrike, the military initially claimed the hospital had been collateral damage in a bombardment intended to protect U.S. forces.

Later, offering little detail, the top U.S. commander in Afghanistan, Gen. John F. Campbell, changed that account. He said the bombardment came in response to a request from Afghan forces for an airstrike, claiming that they had come under attack by Taliban fighters in the area. Doctors Without Borders has repeatedly denied those claims.

Since the attack on the hospital, Afghan officials have suggested that it was justified, claiming that the complex had become a Taliban stronghold in Kunduz after the militants seized the city in September.

But hospital officials have said that is untrue. As a neutral hospital, the organization said it treats wounded patients without regard to which side they fight on. It enforces a strict no-weapons policy within the hospital.

At the news conference, Stokes described how the organization received an email from a U.S. military official in Washington two days before the bombing inquiring about a large number of Taliban "holed up" in the hospital and about the safety of the hospital’s staff.

Stokes and colleagues warned reporters against reading too much into the emailed question, however, saying the organization simply responded that the hospital was full of patients, including civilians, members of the security forces and wounded Taliban combatants.

Two of those Taliban patients might have been high-ranking insurgents, based on the number of fighters who had escorted them to the hospital as well as the intense interest shown in their health by visitors, according to the group’s report released on Thursday, detailing what the organization had learned from interviews with staff members.

The organization said none of the Taliban or government security forces were armed when they entered the hospital and, additionally, were no longer considered combatants and were protected as a matter of international law because of their wounds and subsequent hospitalization.

Military officials in Kabul have declined to answer questions about the airstrike, saying answers will have to wait while the military conducts its own investigations. One is a joint NATO-Afghan inquiry, and the other is being conducted by the U.S. military.

One section of the new Doctors Without Borders report detailed frantic efforts during the airstrikes by the group’s staff members in Kunduz, Kabul and New York to call and text their contacts in the U.S. military and NATO to try to get the attack halted.

The staff at the hospital could hear the propellers of the gunship circling above, firing on the hospital in roughly 15 minute intervals, a total of five passes. Some staff members said several people fleeing the central hospital during the attack came under fire as they tried to reach different areas of the compound.

The first call to military contacts occurred at 2:19 a.m., and the calls and texts continued for an hour, more than a dozen in all. They seemed to accomplish little, according to a log of the calls released by the group.

In one response, a military official with the U.S.-led coalition texted back, "I’ll do my best, praying for you all."

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