here is another area the media often gets wrong
calling the man a student pilot, when in fact he may have already carried one or more licenses or ratings.
in this case he was probably flying with an "instructor" to get familiarized with the aircraft type as pilots normally do
here is a pic of the type
based on the source of the image - this *may* be the accident aircraft
my theory is that the "instructor" was hot-shottin' it a little bit to demonstrate the airplane without realizing his passenger was unbuckled and may have performed a zero g nose over
without a safety belt fastened - everything that is not secured would have done just as in the above video
mid maneuver the man just pulled a superman right out the top of the airplane
considering some models of this aircraft are equipped a canopy opens INTO the slipstream you might find it hard to believe that someone could accidentally open it enough to fall out. (other models feature a canopy that opens from port to starboard being hinged on the co-pilot side.)
but "Zero-G- nose overs" are performed on an arc first marked by a climb followed by a sudden push over and prolonged parabolic sort of decent.
at the "top of climb" at the moment of nose over the aircraft would have been flying at a minimum controllable airspeed not much faster than a stall which for this aircraft is about 40 mph
my second theory is the student was practicing a stall, went into a spin, and was ejected during the instructor's recovery