I've always struggled with writing scenes like these. For example, imagine a situation where two characters, Steve and Alice, are walking down the road. Suddenly, somebody shoots Alice, and she dies immediately. There's absolutely no build-up or warning. There's nothing about the scene that would make the reader even suspect that Alice would die. Steve is devastated because Alice was everything to him.
How do I write scenes like these without making it sound ridiculously dramatic or corny? I feel like using "all of a sudden" is too stereotypical... Any suggestions?