Not very good film quality but it looked to me that he got airborne, seemed to be stable, then a right turn maybe. It didn't look to me like the a/c was stalled, no high nose attitude or "wobbles." Next it appears that the aircraft is flying under control down the tree covered slope before a sudden nose down "push," and then a few seconds later by another "push." Neither seemed to me at least to be the result of stalling while the aircraft was descending, but looked more like deliberate actions. Interference by someone, then maybe a fight of some kind??