My ex is back in town. im afraid hell try to take my kids?

i have been divorced 3 years, i hate my ex with everything in my body, he is a child molester and a liar!! he has been in florida for the last three years, but now he is back, he never calls my kids or sees them, but he is mad i know be is back.. i wasnt supposed to find out and he has already tried to steal my son from me once.. he has no parental rights at all, now because he is in such close proximity to us and is trying to find out exactly where we are... i am afraid he will try something, he has made death threats on me, and has threatened to take my kids.... what can i do?? i have already notified my kids' school and daycares is there any thing else??