The attack occurred in the final hours of a chaotic American withdrawal that ended a 20-year war in Afghanistan.
The Pentagon has retreated from its defense of a drone strike that killed multiple civilians in Afghanistan last month.
The airstrike was launched less than 48 hours after the devastating Isis attack that killed dozens of Afghans and 13 Americans.
Daniel Hale said guilt over participating in lethal drone strikes in Afghanistan led him to leak government secrets about the program to a reporter.
Some employees are disturbed about the potential applications of a project for the military.