Two coalition commandos who were previously believed to have been killed by an Islamic State improvised explosive device were actually killed by friendly fire, a report reveals.

An internal investigation by the British Ministry of Defense (MoD) concludes Delta Force operator Master Sgt. Jonathan Dunbar and Special Air Service (SAS) Sgt. Matt Tonroe were killed by an accidental detonation of coalition explosives.

The two commandos were part of a joint special operations team that was conducting a high-value-target operation in the outskirts of the Syrian city of Manbij. Five others were wounded by the explosion.

A trained sniper, Sergeant Tonroe had been a paratrooper before trying and passing the grueling SAS selection and reinforcement cycle. His death forced the British government to acknowledge the fact British Special Operations Forces (SOF) were operating inside Syria. Previous to that, the British MoD had stated British personnel were confined within the territorial borders of Iraq. Considering the porous nature of the borderline, however, such a “limitation” was not only redundant but also inapplicable. Its sole purpose was to cushion the British government from potential political fallout for having deployed troops inside Syria.

A spokesperson from the MoD made the following statement:

Sgt. Matt Tonroe died from blast injuries caused by an explosion during a military operation. It was initially believed that Sgt. Tonroe was killed by enemy action, however subsequent investigation concluded Sgt. Tonroe was killed by the accidental detonation of explosives carried by coalition forces. Our thoughts continue to be with Sgt. Tonroe’s family and friends.”

Master Sergeant Dunbar also had a remarkable career. He had been awarded three Bronze Stars for Valor, the nation’s fourth-highest award for combat valor, four Army Commendation Medals, six Army Achievement Medals, five Good Conduct Medals, and the National Defense Service Medal, among other awards.

This isn’t the first time Tier 1 special operations units tangled in a green-on-green incident involving explosives. In 2010, Linda Norgrove, a British aid worker who had been kidnapped by the Taliban in Afghanistan, was killed during a hostage rescue attempt by SEAL Team 6 operators. Initially, it was believed that Norgrove had been killed when one of her captors detonated a suicide vest. An after-action investigation, however, revealed the British civilian had been killed by a grenade thrown by one of the Navy SEALs.