US military acknowledges errant drone strike last year killed a civilian, not an al-Qaeda leader

A targeted U.S. drone strike in northwest Syria one year ago Friday hit and killed a civilian, not the al-Qaeda leader it was looking for, the Pentagon said after an internal review.

"U.S. Central Command acknowledges and regrets the civilian harm that resulted from the airstrike," the combatant command said in a statement after the year-long review. It confirmed the Syrian, Lufti Hasan Masto, "was struck and killed instead" of an intended senior al-Qaeda leader. The news was first reported by The Washington Post.

U.S. forces misidentified the target but found that "the strike was conducted in compliance with the law of armed conflict," CENTCOM said in a statement. It also said officers adhered to Pentagon and Central Command policies.

Still, CENTCOM acknowledged that its "investigation revealed several issues that could be improved" and said it was "committed to learning from this incident and improving our targeting processes to mitigate potential civilian harm."

Wes Bryant, a retired U.S. Air Force master sergeant and senior targeting professional in the Middle East, including Syria, told ABC News the Pentagon's public statement indicates officers did not realize they lost the senior al-Qaeda leader they sought, believing they struck their intended target.

"It could have been that the sheep herder had a business or even familial or friend relationship with the senior leader—and so they had some sort of contact prior to the strike, and that during that contact, the targeting cell somehow confused the two," said Bryant, who specialized in collateral damage assessments under Central Command.

"Even if that were the case, contact with an enemy combatant as a civilian, whether in a business capacity or a familial or friend capacity, does not make one a combatant. To be a combatant, one must be actively contributing to or participating in combat operations."

In general, an adult male herding sheep would represent a "yellow flag" to military targeters, Bryant said. Investigators likely concluded personnel acted in compliance based on a "fog of war" explanation.

"U.S. instances of civilian harm and botched strikes such as this have been the exception over two decades plus of warfare, which has largely been dominated by strike campaigns," Bryant said.

CENTCOM made no mention of potential disciplinary action and did not disclose issues it found, citing classified information that can't be shared.

ABC News' Anne Flaherty and Matt Seyler contributed to this report.