He also plotted to kill his step mother. The young man had severe mental health problems. He came from a broken bitter home. Those characteristics are not misogyny
I don’t know his parents or anything about their real situation, but one thing to bear in mind is that having a mentally ill child, especially now that it’s so hard to get treatment for him, puts a huge strain on a marriage. He was diagnosed as having some form of mental illness or problem at a very young age, and when that happens, the the life of the entire family begins to revolve around this child and there often is a lot of conflict and anger.