How to remove someone from a rental who is not on the lease

[Oktay Ugur]

My tenant just informed me that her and her boyfriend got into an argument and things got a bit physical. She claims that she doesn't feel safe living there and the boyfriend refuses to leave the property. He is not on the lease and she wants to continue to live at the property. Currently, the tenant is staying with her daughter and the boyfriend is still at the property.

What is the best way to deal with this as a landlord?