Matt Barker writes:

He was getting ready to land the tug yesterday evening and it spun
in and we lost Mark.

.

An eye witness reports:

Buzzing the field low to drop the tow rope after a busy day towing. Suddenly
the nose went up very steeply, the plane turned left, three spirals then impact.
Dragonfly hasn't been moved. Not sure if linkage broke or what happened to cause
the nose to rise up.

So this could be an issue of the plane breaking.

http://youtu.be/7grt7p_GsVQ

http://youtu.be/Lg8z58xbuRw