If it's any consolation, the tree isn't dead. Sycamores have an amazing capability for regrowth from the roots or stump itself. However, it will of course not achieve its previous grandeur within the lifespan of anyone alive today.

So I’m looking at he first photo and the local constabulary only believes it might have been vandalism.

In all of recorded history has there ever been a case of a tree just shearing itself off for no reason?

I’m also in the camp of making the bastards responsible for this pay dearly for the same age as the tree