Italian NH90 crash in Bracciano Lake during a demonstration

What happens in this video ?

This Italian army NH90 helicopter crashed in the Bracciano Lake during a public flight demonstration on June 1st 2008, killing the pilot. The other 2 people on board were rescued and survived the injuries. The helicopter was at the end of its display in the Ali sul Lago airshow, at Vigna di Valle airport, when it touched the surface of water and broke up in many pieces before sinking.