Racist Tenants - how to address or ending lease an option?

[Kim Huynh]

I have tenants who are racist to other tenants who live on the property.  Both tenants has made racist comments about the other tenants to my property manager when referring to the other tenants.  One of the tenant went as far as to say he's going to get his gun and shoot them.  When the property manager told him he can't say things like that, he plays it off saying he can say whatever he wants but he doesn't always mean it.  What can we do?