Marine Lt. Gen. Richard Mills, left, commander Marine Forces Reserve and Marine Forces North, speaks with Maj. Gen. Glenn H. Curtis, adjutant general of the Louisiana National Guard, during an Aug. 4 meeting at Jackson Barracks in New Orleans. The Defense Department Inspector General’s office has launched an investigation into Mills’s handling of a controversial legal case tied to an insider attack in Afghanistan. (Photo by Master Sgt. Toby M. Valadie/Louisiana National Guard)

The Pentagon’s top watchdog organization has launched an investigation into whether a three-star Marine Corps general retaliated against a lower-ranking officer who warned Marines in Afghanistan about a potential threat posed to them by an Afghan police chief 17 days before an on-base shooting killed three of them.

The Defense Department Inspector General’s office opened the investigation against Lt. Gen. Richard P. Mills, commanding general of Marine Forces Reserve and Marine Forces North, of New Orleans, according to an Aug. 19 memo sent from the IG’s office to the lower-ranking officer, Maj. Jason Brezler. The watchdog will examine whether Mills violated the Defense Department’s directive guaranteeing protection to whistleblowers in the military by ordering Brezler to appear before an administrative board that met in December 2013 and recommended he be discharged.

Mills, who commanded all Marines in southern Afghanistan for a year spanning 2010 and 2011, did not respond to an e-mail. A spokesman for the general, Adam Bashaw, referred comment to the Defense Department IG. Bridget Serchak, a spokesman for the watchdog, said the office as a matter of policy does not confirm if investigations are ongoing.

Brezler could not be reached for comment, but a lawyer for him, Kevin Carroll, said they believe Brezler became the target of retaliation after he communicated with Congress and law enforcement after an Aug. 10, 2012, killing of three Marines at Forward Operating Base Delhi in Garmsir, Afghanistan.

Before the shooting, Brezler sent classified information on July 24, 2012, to Marines in Garmsir about a police chief, Sarwar Jan, that he had encountered during a previous deployment. The Afghan official was believed to have ties to the Taliban and had been removed as the police chief in another district while Brezler was deployed in 2009 and 2010. He was later put in power in Garmsir anyway by the Afghan government.

The move prompted deployed Marines to ask Brezler, a reserve Marine who works for the New York City fire department, for information. He sent a document labeled “NATO SECRET” about the police chief over an unclassified Yahoo! e-mail account in 2012, and reported his own mistake shortly afterward, according to Brezler’s lawyer and documents obtained by Checkpoint.

The shooting was carried out afterward by a teenager working for the police chief, Marine officials say. Identified by the Marine Corps as Ainuddin Khudairaham, he was convicted of murder in July and sentenced as a minor to 7 1/2 years in confinement, upsetting Marine family members who expected a tougher punishment.

A lawyer for Maj. Jason Brezler, seen here during a deployment to Afghanistan spanning 2009 and 2010, says he was retaliated against by a Marine Corps general for speaking with Congress and law enforcement about a 2012 insider attack in Afghanistan that killed three Marines. The shooter was a teenager working for a police chief, Sarwar Jan, whom Brezler had struggled with while deployed. Jan is depicted above at right in the cap. (Photo handout courtesy Kevin Carroll)

The case drew interest on Capitol Hill. Rep. Peter King (R-N.Y.) sent the Marine Corps’ top officer, Commandant Gen. James F. Amos, a letter in July 2013 asking why Brezler received a bad fitness report after sending the warning to deployed Marines.

Mills wasn’t directly involved at the time, but the following month ordered Brezler to appear before an administrative panel of officers known as a Board of Inquiry to determine if Brezler should be ousted from the Corps for mishandling classified information. Mills had no direct involvement in the incident in Afghanistan or its subsequent handling, but oversaw Brezler as the Marine Corps’ top general overseeing reservists.

The board ultimately decided in December 2013 that Brezler should be separated from the Marine Corps. Marine officials speaking against him at the hearing said an investigation by the Naval Criminal Investigative Service determined that he had more than 100 classified documents in his possession, and planned to use some of them in a book he was writing. Brezler maintained he had brought them home from Afghanistan inadvertently because he and fellow Marines did not have enough computers and used their own for professional purposes.

Some senior Marines rallied to Brezler’s defense ahead of that hearing. Mills told at least one of them that they did not know the whole story, and Brezler “could have been court-martialed” for his mishandling of classified information after returning from Afghanistan, according to e-mails published by this reporter last year for Foreign Policy. That has not occurred.