Lock my mother's violent boyfriend out of the apartment?

My mother has had an abusive boyfriend for years. I've suffered greatly because of it. (Both are alcoholics; I'm moving out soon with the help of the youth welfare office.)

Anyway, the police were here today because I called. Ultimately, they couldn't lock him out for the following reasons:

He only “almost” hit her (he wanted to swing, but my mother defended herself)

In the end, there was nothing they could do about it.
The friend has now gone somewhere (he continued to harass us after the police left), and I've locked the door so he can't get in. (He has his own key, but he can't get in like that.)

The rental agreement is for both of them.
For these reasons, I've essentially locked him out of the apartment, and my question is, am I allowed to do that? It's pretty self-explanatory, but my mother and I are worried that he'll continue to harass us and not leave us alone. Can he just call the police himself and report it?