According to Cyber Berkut, the video had an accompanying message, stating the the footage was filmed near the village of Shirokino and warning that all separatists - 'traitors' to Ukraine - would face the same fate.
Cyber Berkut has been releasing leaked documents, audio, and video for the past year or so. They're the ones who released the phone call between EU High Representative for Foreign Affairs Catherine Ashton and Foreign Minister of Estonia Urmas Paet, in which they discuss the Maidan snipers. (You can see a list of some of their leaks on Wikipedia.) The video was then publicized by LifeNews in Russia, who confirmed its authenticity. LifeNews tends to be rather sensationalistic, but that does not necessarily imply the video is a fake.
That said, the authenticity of the video has not been confirmed. The DPR has so far refused to comment, and pro-Kiev websites are denouncing it as a Kremlin-produced hoax. Colonel Cassad is still on the fence. Azov is no stranger to torture. They're the ones who branded a swastika onto this Donbass resident.
On the one hand, Rozhin [Col. Cassad] points out that it's not as if there have been no cases of torture by the various neo-Nazi groups in Ukraine's official service (see photo above for an example--more at the link). Moreover, given the reputation of Cyber-Berkut, it seems unlikely that the organization would engage in spreading of false information. On the other hand, Rozhin acknowledges it's possible Cyber-Berkut got trolled by a pro-Kiev organization, which deliberately posted a fake clip so as to discredit CB.That makes more sense than the predictable "Kremlin propaganda" nonsense.
The final possibility is that the clip is genuine, and the trolling claim is intended to depict the real video as a fake spread as misinformation. Keep in mind, however, that Novorossia media have fallen for fakes spread by the UAF before. The most notable was the story of a Novorossia nurse by the name of Sasha Serova being brutally murdered by the UAF, accompanied by a photo of...US porn star Sasha Grey (which is what the name Serova can mean). Therefore one has to approach such stories with particular care.
Real or not, people need to realize something: Azov, being the psychopaths they are, are perfectly capable of doing such a thing. As shown above, Azov has engaged in the most despicable acts of torture and murder possible. But many will deny the authenticity of this video not based on any evidence, but simply because they can't believe such a thing is possible. "They wouldn't do that, therefore they didn't. Only fanatical nutjobs like ISIS are that brutal."
Sorry, but that's just wrong. It doesn't matter what country you're from, what nationality you are, what religion you follow -- psychopaths are just as brutal, remorseless and monstrous. It just doesn't suit the West's geopolitical interests to admit that Azov -- who fights on the side of "our" guy, Poroshenko -- is the Ukrainian psychological equivalent of ISIS. It is. It's the same sickness: psychopathy.
Actually, the connection is even clearer than that. Azov are "our guys". They're the ones effecting the U.S.'s will in Ukraine. As it just so happens, that is exactly what ISIS is doing in Syria and Iraq and Yemen, where they are being used to fight against the Houthi rebels that ousted the US-backed puppet president Hadi.