Sometimes to make a death feel really sudden and / or shocking, I've seen it happen in a single sentence or just a few words. You've been with this character for the whole book, and then gone. Way too fast to register, it always makes me do a double take. The abruptness really makes it feel real, although of course this isn't best for all stories, and I'm not really a writer, just a reader :)
good luck on your book!