In my current WIP I have a scene where a man falls backwards into a chair in which a broken mirror had been placed; a large shard of glass stabs him in the back. I intend it to be fatal.

Would he have time to register shock? Would he have time to scream, or even grimace? Would he start spitting up blood?

I can think of a movie scene where someone was killed by a jagged piece of glass in a falling window sash, but the afterlife was a main plot theme and we see his reaction after he's dead.