A top U.S. military commander revealed Wednesday that the investigation into the airstrike on a Medecins Sans Frontieres-run hospital in the northern Afghan city of Kunduz has concluded that the incident was a tragic accident caused primarily by human error.

"This was a tragic mistake. U.S. forces would never intentionally strike a hospital or other protected facilities," U.S. Army General John Campbell, the commander of international and U.S. forces in Afghanistan, said at a news conference where he announced the results of the investigation, according to Reuters.

The attack killed 22 people, including 12 MSF staff.

The investigation found that the crew onboard the AC-130 gunship misidentified the hospital they were targeting several hundreds yard as the building they were supposed to hit, Cambell said, reported USA Today. Noting that the aircraft left 69 minutes early and were not fully briefed as to which targets were deemed "off-limits," Campbell said that those closest to the incident were suspended from their duties.

The U.S. military confirmed that officials from Medecins Sans Frontieres, also known as Doctors Without Borders, had contacted U.S. military officials 12 minutes after the attack began, saying that they were under attack, according to The Hill.

Brigadier General Wilson Shoffner, the deputy chief of staff for communication for international forces in Afghanistan, said that the AC-130 gunship had ceased its assault on the MSF facility once the U.S. forces realized their mistake.

"The investigation found that some of the U.S. individuals involved did not follow the rules of engagement," Shoffner said.