WARNING: This video shows a deadly helicopter crash – viewer discretion is advised.

This video of an Mi-28N “Havoc” attack helicopter at a recent Russian airshow shows the worst possible scenario for any flight demonstration. A loss of control of the aircraft and then a fiery crash.

Unfortunately for one of the two crewman, the crash was deadly. The other somehow managed to escape the wreckage without any major injuries. They were both members of the Russian Golden Eagles aerobatic display team performing at the Aviamix airshow near Ryazan.

The cause of the crash is still largely unknown, but there are a few indicators into what sent the giant, state-of-the-art chopper into a tailspin that couldn’t be righted.

This from Foxtrot Alpha:

RT reports that in a statement from the Defense Ministry’s press service, the cause of the accident seems to be known:

“According to preliminary report of the hospitalized pilot of Mi-28N, when performing an aerobatic stunt, the emergency alert system of the helicopter reported the failure of the hydraulic boost system.”

As a result, all of Russia’s roughly 100 Mi-28s have been grounded until a deeper investigation into the incident can be made. The Mi-28 was supposedly designed with an ejection seat system that fires its crew out the side and downward. It is not clear if using such a system would have saved the pilot’s life in this case or if it is even operationally in use.

The fact that the ejection system wasn’t used is curious, and would obviously tip toward a mechanical failure. It’s clear from the video that the pilots would’ve had at least a few seconds to initiate the evacuation if the copter was still functional.

It’ll be interesting to see if Russia discloses the failure in the coming days while their entire Mi-28 fleet stay grounded. Or if they just keep mum and fix it internally.