Members of Doctors Without Borders have taken to calling the incident a "war crime."
The executive director of the UK branch of Doctors Without Borders, Vickie Hawkins, dismissed Campbell's explanation in an interview with Public Radio International, echoing earlier statements from the organization on how they see the incident.
"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," Hawkins told PRI.
The charity said that the main hospital building in the sprawling compound, "where medical personnel were caring for patients, was repeatedly and very precisely hit during each aerial raid, while the rest of the compound was left mostly untouched." It earlier said that bombing had lasted an hour, and repeated calls to NATO and the U.S. military to call off the strikes had failed.
On Sunday, the organization announced that three injured hospital patients had died, bringing the total death toll to 22, including 12 hospital staffers. It earlier said that three of the dead were children in the intensive care unit. The charity also announced it was withdrawing from Kunduz.
Afghan officials said earlier that helicopter gunships had returned fire from Taliban fighters who were hiding in the hospital. But Kate Stegeman, the charity's communications manager, said there were no insurgents in the facility at the time of the bombing.
The attack was a "grave violation of international humanitarian law," it added. The MSF statement made no mention of whether Taliban fighters were present in the hospital.