If you have health insurance, you need to call in to get a psychological examination. They'll ask you a couple of questions over the phone to find out about the severity of the situation. One of them will be about suicidal tendencies. When you say yes, they'll ask a few questions to figure out how far it's gotten--plans, attempts, and so on. Be honest, and be sure to mention your anger issues and the ensuing assault and battery (as long as you're a minor, which I presume you are). You need to get front-loaded to the top of their slate.
Then you get an appointment, likely as soon as they can get you one, and go in. They'll have you fill out a big clipboard of questions about symptoms and things like that, some questions ranking how you feel about certain things and how worried those things make you, previously diagnosed psychological conditions and so on. It's tedious, but it's not especially difficult. Mostly just checking off a lot of boxes. Then you go in, probably to a room with nice lighting and a few different places to sit, you sit down, you talk for a while, you find out where you are and what needs to be done.
This will be scary, but it is better by far to reveal the truth as soon as possible.
If you don't have health insurance, I'd almost considering turning yourself in. You're young. You'll get as much help as you need, so do it now.