Hello and welcome to JustAnswer. Please note:This is general information for educational purposes only and is not legal advice. No specific course of action is proposed herein, and no attorney-client relationship or privilege is formed by speaking to an expert on this site. By continuing, you confirm that you understand and agree to these terms.
I am very sorry to hear about this situation. No, I am afraid that the landlord cannot be sued for the actions of their tenant in most cases. Simply put, the landlord is not liable for the actions of a third party (i.e. the tenant) - they cannot be held liable for what their tenant does.
The only exception is if the landlord knew with certainty that the tenant would be violent/threatening. What this means in legalese is that the Plaintiff (i.e. you) would have to show causation, and a third party's actions break causation unless it was foreseeable (see HERE). This is generally very hard to prove.
So I am afraid that the landlord is not liable, likely. Of course the tenant is and may be sued for a number of causes of action, however, and not just for an injunction/restraining order.
Please note: If I tell you simply what you wish to hear, this would be unfair to you. I need to be honest with you and sometimes this means providing information that is not optimal. Negative ratings are reserved for experts who are rude or for erroneous information. Please rate me on the quality of my information; do not punish me for my honesty.
I hope this helps and clarifies. Please use the SEND or REPLY button to keep chatting, or please RATE when finished. You may always ask follow ups at no charge after rating. Kindly rate my answer as one of TOP THREE FACES/STARS and then SUBMIT, as this is how experts get credit for our time. Rating my answer the bottom two faces/stars (or failing to submit the rating) does not give me credit and reflects poorly on me, even if my answer is correct. I work very hard to formulate an informative and honest answer for you; please reciprocate my good faith with a positive rating.