Ouch. Broke up in mid flight? Keenly interested to see what the cause is.
RIP, gents, another "routine training mission" ends up with loss of brothers in arms.
EDIT: I looked through the photo gallery. That isn't just the blade that is detached from the helicopter. Still attached to it are what look to be parts of the hub and the blade grip/retention. (Terminology may be off due to me not being familiar enough with that aircraft's nomenclature for those parts). From the pictures of the blade and attached elements, I am wondering if the blade strap had a failure, or if something else failed and this blade, plus hardware, went one way and other parts went elsewhere with the main body of the aircraft ending up in the water. Cant find my old TM, nomenclature still probably wrong.
EDIT 2:
From this picture, I am not sure if that is showing a part of the mast attached or not. It does appear that one blade with attaching pieces is lying next to the fence, and the attaching bits without a blade are attached to all that.