In a statement, Doctors Without Borders, which had previously called the attack a probable war crime, said the report was "shocking" and left "more questions than answers."

Gen. John F. Campbell said the strike was "tragic, but avoidable." Human errors compounded by technical malfunctions onboard the AC-130 attack aircraft caused the strike, he said, speaking to reporters at the Pentagon in a video broadcast from Kabul.

The military investigation found that the "cause of this tragedy was … avoidable human error, compounded by process and equipment failures," Campbell said.

Campbell addresses reporters in this CNN video: