The Pentagon is promising an investigation today after it was revealed that an AC-130 warplane carried out sustained fire against a Doctors Without Borders-run hospital on the outskirts of the Taliban-held city of Kunduz, killing 16 including 9 staffers and three children.

The hospital was already overwhelmed by the huge number of casualties from the past week of fighting over Kunduz, which the Taliban seized Monday. Doctors Without Borders is demanding clarification on what happened, noting they contacted the US after the first strike near their hospital to warn them it was so close, and sustained attacks against the hospital continued for over 30 minutes after that.

The US Embassy in Kabul expressed “condolences” but did not apologize for the attack, while both the UN Mission to Afghanistan and the Red Cross condemned the strikes, saying it was unacceptable to undermine humanitarian organizations in the warzone.

Though Doctors Without Borders reported 16 dead and 37 injured as a preliminary toll, they added that 30 other people are unaccounted for, meaning the tolls will almost certainly rise in the hours to come.

This is not the first time the US has come under fire for its actions against hospitals in Afghanistan, though it is by far the biggest such incidents. Back in 2009 there were a pair of incidents, including one in which US ground troops attacked a hospital, forcing their way in, and tying up the staff before smashing up the place. That hospital was run by the charity group the Swedish Committee for Afghanistan.