4 year old cat keeps attacking and stalking my female cat

[4catdad]

I have 3 male cats and 1 female cat. The youngest is a 4 year old ragdoll cat who is neutered. The older female cat is spayed. She is a very tiny cat. The other cats dont bother her but the 4 year old randomly throughout the day stalks and attacks her. He urinated all over our couch and on the bathroom floor. He is very loving with us and the kids and one of the other male cats. I dont know if its behavioral, hormonal or medical. If anyone has any information or has experienced this please I would appreciate some help.