Preliminary NTSB report:
http://images.bimedia.net/documents/...TSB+Report.pdf
Better quality video with coment:
A Stinson 108-3 with a 165 hp engine is definitely not designed to climb with 4 occupants at a density altitude of almost 9200 feet.
The shocking part for me is, that the pilot elected to fly into the trees after trying to gain altitude for ages over relatively flat terrain. He could have put it back onto the ground with minimal or no damage to the airplane at any time before flying it into the forest area.