Russia’s military and private mercenaries are known for their brutality. Over the weekend, the world got another example when a video titled “Hammer of Retribution” was posted recently to the Grey Zone Telegram channel.

In the video, a man is seen with his head taped to what looks like a concrete wall. The man said his name is Yevgeny Nuzhin. He said he was captured on Nov. 11 in Kyiv by Russian forces and was told he would face trial.

Those were his last words. A person standing behind Nuzhin in the video smashed a sledgehammer into his neck, dropping him to the ground. Nuzhin was struck again in the face with the sledgehammer before the video cuts out.

Nuzhin was serving a life sentence for murder in Russia before being recruited to fight in Ukraine by the Russian Wagner Private Military Group. Nuzhin was captured by Ukrainian forces in September and reportedly started fighting against the Russians shortly thereafter.

Western news outlets can’t verify the authenticity of the sledgehammer video. Yevgeny Prigozhin, also known as “Putin’s Chef”, gave credence to the footage.

After years of harsh denial and lawsuits claiming otherwise, Prigoshin recently admitted he founded the Wagner Private Military Group in 2014. Wagner mercenaries are being used to bolster Russia’s military forces in Ukraine, which are suffering heavy losses.

Prigozhin said the video should be titled “A dog receives a dog’s death”, and called Nuzhin a traitor.

In a not-so-veiled threat against anti-war dissenters in Russia, Prigozhin said not all Russian traitors are on the battlefield. He said some are “holed up in offices” or using their own business jets to leave the country.

Reuters contributed to this report.