She wasn't his wife. She was trying to distance herself from him, and he was obsessed with her. basically, if he couldnt have her, noone could.
For all of you who made jacobs out to be a good guy, hope this changes your mind. He was nothing but a lying, decieving rat bastard, who took the cowards way out, and took an innocent life with him. May he rot in the bowels of hell for eternity!!!