That's a very frightening piece of footage indeed. I don't understand why he didn't put her down immediately when it was evident that performance was insufficient. You could see it wasn't going to end well just looking at pilot's attempts to lift off...
According to NTSB prelim report (link below), the flight was operated near Bruce Meadows Airport (U63).
Elevation 6370 ft..
NTSB preliminary report
EDIT: Maximum temperature
on that day, in that region was 28°C recorded. That would put them at over 9000ft density altitude. Owch.