(CNN)Acting Secretary of Defense Patrick Shanahan is seeking to tap a senior US military officer to oversee possible punishments and re-open the probe relating to the 2017 Niger ambush that left four US soldiers dead, a move that has caught several senior officials by surprise.
Shanahan's efforts to reopen Niger probe surprise military officials
Five administration and military officials with direct knowledge tell CNN that Shanahan's efforts are designed to possibly open the door to potential criminal charges being brought against those personnel who were involved in the incident.
The move is part of an effort to review all the findings related to the Niger probe prior to Shanahan's signing off on any proposed non-criminal punishment for the service members involved.
Shanahan's efforts come nearly a year after the completion of the first fact-finding investigation into the incident and several months after military commanders provided their own recommendations to then-Secretary of Defense James Mattis as to what punishments should be issued.
In an unreleased memo described to CNN, Shanahan is calling for a fully independent review by a so-called Consolidated Disposition Authority, a military designation that allows a senior military officer to fully review a matter and ensure accountability actions including possible criminal charges or other administrative actions.
While Shanahan initially intended to tap Gen. Michael Xavier Garrett, the commander of US Army Forces Command, to serve in the role, even signing an unsent memo Monday designating him as such, he has since changed his mind and is seeking a new officer for the post, according to an administration official directly familiar with the effort.
Two administration officials emphasized the potential change had nothing to do with Garrett, but said the Pentagon may be considering picking an officer with legal experience.
The person appointed "will have full authority" to take legal actions, the official said, adding that the appointment is expected in the next several days.
This latest move is only the most recent development related to the ambush and comes after several months-long investigations and reviews into the affair have already been completed by various military commands.
Shanahan's new plan caught several military officials by surprise and has raised the ire of some officers in the Army and Special Operations Forces community who say that no criminality had been found during the various investigations.
The Army Chief of Staff, Gen. Mark Milley, and the Secretary of the Army, Mark Esper, only learned of the new effort on Tuesday, the same day Shanahan told Congress that he had ordered a new review, according to an administration official.
"When I came into this role, the recommendation was brought to me that Secretary Mattis had, he had convened a review, and that recommendation was brought to me. I did not find that sufficient, so I convened my own review, so I can ensure from top to bottom, there's the appropriate accountability. I do not know when that will be complete, but I have to assume that much of the work that's been done to date can be used," Shanahan told a hearing of the House Armed Services Committee.
A defense official told CNN that Shanahan's latest efforts have been "tightly controlled" by Shanahan's office due to previous leaks to the media about the status of the investigation and punishments of those involved in the incident.
"Any leaks could damage the integrity of the investigation," the official added.
Shanahan told reporters at the Pentagon Tuesday that he would "clarify" his comments on the re-opening of the Niger probe via a statement on Wednesday, however no statement has been issued.
Officials say Shanahan ordered the newest review because of his reluctance to sign pending recommendations for non-military punishment without an additional examination.
Unlike his predecessor James Mattis who as a former Marine general once led a military combatant command, Shanahan, a former Boeing executive, has had little experience with such investigations and the issuing of punishments.
Defense officials t