Tenant vs tenant what is required?

[Mike R.]

we have a tenant that claims another tenant is harassing her (looking in her windows, taking videos etc). We have witnessed none of this behavior.  The tenant that is supposedly the harasser claims the other tenant is up to no good, funny smells coming from her apartment (she even called the police about the smells--police found nothing unusual and neither have we).   we do not want to get involved with disputes between tenants but the one claiming harassment is considering leaving and filing a police report etc. what are our obligations given we have not seen any of the behavior?