Witness an unusal cut!

[pdqdl]

Without seeing it, it sounds like an open face Humboldt notch with a bored backcut. Leaving just enough hinge to commit the tree over center and break off, thus the butt sliding down the Humboldt and off the stump first.

That's exactly what I was thinking.

You can exaggerate the slide by making a 1/2 trunk diameter (or greater) face cut that slopes steeply downhill. The narrower the face cut the sooner it closes and breaks, and the more severe the slide action will be. The back cut should be done with a steeper angle than the face cut, so that no shoulder is left on the stump to hang up when it starts sliding.

Murph shows this effect exactly in the link he posted above. (of course, I have no idea how he made the cut)