Experts say it was probably a compressor stall on #1 engine. The supersonic air coming from overflow panels on top seems to indicate this but it also adds to the puzzle. 
 
Incredible photos from last Friday’s accident in Lethbridge.
Looks like the left engine has the nozzles open so that one either in AB or flamed out. Cool sequence of the rocket seat coming out, the canopy leaving the scene, the chute opening sequence and the separated seat falling away…technology is great! The impact photo has flame shooting out of the left engine…adds to the puzzle