While Ukraine’s military has been successfully chasing Russian troops out of one territory after another, Vladimir Putin’s foot soldiers have apparently been turning their weapons on each other as the Russian leader’s “special military operation” continues to come apart at the seams in spectacular fashion.

The Kremlin’s flailing bid to get an edge on the battlefield by deploying mercenaries from the Wagner Group—which now includes hundreds of prison inmates—has reportedly backfired as the private military force butts heads with the Russian military.

The growing conflict resulted in a Wagner fighter gunning down a lieutenant colonel in the Russian army—a deadly episode of “friendly fire” that the Kremlin is said to be trying to sweep under the rug, according to the human rights group Gulagu.net.

“They are trying to hush up the incident and prevent publicity. And this is not the first emergency of its kind,” the group quoted a source as telling the Gulagu.net hotline.

The incident was also reported by two other Russian Telegram channels, though no details were provided on when or where the shooting is said to have taken place.