I'll Break Every Window In The House!

I have a 17-year-old son that has become increasingly defiant and angry with me (his mom), although I don't understand why because I've always been his number 1 supporter. Well, he skipped a couple of classes yesterday at school, so I gave him three days of grounding. He said he couldn't be grounded, because he had plans already established with his friends. I told him he would have to change them, that I expected him home after school. He said "no" - and he didn't come home after school. He called me and told me if I decided to call the police to go find him, that "I" would face his wrath of him breaking every window in my house (he's never exhibited violence before). He has recently began saying "F__ you” to me, like it's normal behavior. I turned off his cell phone because of it, but it has made him even angrier. I've read through the ebook, but either missed it, or didn't understand - how do you even begin to start pu...