Sooo I need some help...

Okay so I'm no lawyer here but let your "friend" know these few facts: (I'm using you in reference to your friend)
- Being under 18 allows you to be charged as a minor, but every case may be escalated to an adult trial if it passes through a certain hearing; when you are 18 or older, you do not have an option to be tried as a minor
- Don't say anything - nada, zip, zulch, zero - you have the right to remain silent (I assume that he's in the USA?), so don't say anything until a lawyer is there who can (maybe at best) help you
- Cops will say it's okay to tell them everything and that they're your friend. If you know you did something wrong, then don't say anything. Innocent people stay quiet too so they don't self-incriminate themselves by accident you know.
- Lastly, just remember, you did nothing wrong