Help! My new male cat is attacking one of my female cats.

I got a new kitty (a rescue between age 1–2) in early August and we’re having a rough time adjusting. He was isolated for 2–3 weeks with a screen door in between. He has been roaming free for the past 2 weeks. He is respecting my 13 yr old female, but he is repeatedly attacking my 7 yr old female. This morning he jumped her and ripped out lots of her fur. She is living in constant fear. Is there anything I can do short of finding him a new home?