That's always the most dangerous time for a woman in a failing relationship. She decides to go, he finds out, wham. (Not saying that happened here, just general speculation.)
But Bonne, if that were true, knowing what we know (or think we know...!)why wouldn't he just let her go? Why kill her?
It may be just the opposite with Laci angry and pleading to a cheating husband that led to a violent end.