Truck loading boulder falls off cliff - GIF

[Frank S]

That looks like A HIAB crane, and it was either old or poorly maintained. There are 2 cylinders and a leaf chain that makes it rotate while 1 cylinder is pressurized to pull the crane while the other is pressurized to prevent overswing. The truck must have been set up with the outrigger holding the loading side Higher than other side allowing for the load to become over centered the other swing cylinder should have prevented it from having a sudden accelerated swing which it did not prevent. maybe there was internal leakage in the poppet valve or the seals on the cylinders leaking.
The operator may or may not have been able to prevent this by suddenly momentarily reversing the swing arresting the movement of the load. He might have even tried but experienced a delayed signal activation from his remote.
Whatever the cause someone had a really bad day.