Very sad indeed. The ejection seat in the Hawk (what the Red Arrows use) are designed to be "Zero/Zero" seats. That means that an ejection "should" be survivable from zero airspeed at zero altitude. In the PC-9 (which I used to fly) it was a "Zero/80" seat (from memory). Which means an ejection was survivable at Zero feet and 80 knots.
The method of going through the canopy varies from aircraft to aircraft too. In the PC-9, the seat had "horns" which would break the canopy on the way through. The Red Arrows have "det cord" in the canopy, which is a small explosive cord in the canopy which shatters it before the seat goes through.
There are many injuries that can result from an ejection, these can include "flail" injuries, dynamic overshoot, broken femurs, neck and back compression, and then you have to land.
My thoughts are with his family and team members.
FatBoy