Strictly that is not a crack, it is a tear. A matter of insufficient ductility in that particular case. It didn't fail sizing, it failed on firing, and invariably on the first firing. Happens with both new factory loaded ammunition and component cases. Most likely cause is, as Ole Joe Clark said, it missed the final annealing leaving the case too hard. This happens with all brands of brass.
Might be your first, if you shoot for any amount of time it will not be the last! Throw it away and get on with life.