from what I can see in the pics it looks like the throttle side of the mount broke last and since you said it went to full throttle the prop may not have exploded right away but instead warped during the vertical. I have had some plastic props off of toys that I stuck on my 30,000 rpm rotary tool and the pitch of the prop causes the tips to bend forward slightly. This often causes the pitch of the prop to be disturbed for a moment increasing the rpm's. After a few rounds centrifugal motion takes over and the prop straightens out. the loud sound you heard may have been the increasing rpm's of your engine then upon the staightening out phase the prop may have broke. If my theory is correct the increased rpm's and the propellers warping caused a lot of vibration and that is what snapped the engine mount.