They rarely leave easily or the first time. My ex had a hard time staying gone. This is an awesome time to right down your boundaries and the consequences for violating them if he shows up again.. It makes it easier to follow through on your plan.
911 is a great answer if he threatens you in anyway. My ex did not like that one bit. I never actually had to dial it. I just held the cell phone in my hand with my fingers poised on the buttons in case I needed too.