Match Point starring Scarlett Johansson and Jonathan Rhys Meyers

Why did Jonathan Rhys meyers character Chris kill Scarlett Johansson character Nola? It seems like he truly loved her and had a stronger connection then Chris and his wife. Why wouldn't he just leave his wife to be with Nola especially after finding she was caring his child. It seems like to me that Chris to be haunted with what he has done for the rest of his life. I think all the characters would have been happier if Chris left his wife to be with Nola. Why did Chris kill her instead?