When you start considering one plot scenario and an exciting twist occurs to you, and then another, and you start twisting things around until you wind up with something like a baseball game with several teams and about 10 bases. Oh, and something like four home plates.
Recipe for (in this case, suspense/crime) plot confusion:
original death premise
kill witness option
take neighbor hostage option
him see her meet another man option
That's all before adding a pinch of plot resolution and a dash of interesting but conflicted characters. Stir well and read!