That kind of sympathy is unusual on this board... it was you wasn't it JulieFlyGirl?
Another plausable scenario which fits with the pilot's story is that it had been running but he shut it down when he noticed the tie-downs. Prop stops not far from TDC and he bumps it just enough to push it over the top.
Reason he was taxiing at night in crap weather? Because it was crap weather and he wanted to move it to a safer spot (hangar?)
He's lucky he didn't get chopped up.