Pilot Killed In L-29 Crash At Reno - AVweb

"Hogue’s aircraft was turning at high speed when it lost altitude at high speed and exploded. "
Makes it sound like an in-flight explosion when put that way.

The pilot did not recover from the the descent, and the aircraft impacted the ground in a steep turn, while apparently structurally intact.
Technically at this point it did NOT explode, but the suddenly breached fuel tanks did result in a rapid burn of the remaining fuel (headlines like to use the term ‘fireball’), as is typical in a destructive impact of this kind.

Very sad to see. Given what appears to be a sudden high-G pull immediately prior to the beginning of the descent, it may be a case of G-LOC.