I'm having trouble understanding your question.
If a twelve year old sent you pornographic pictures and you did not request them, then you have committed no crime, and should destroy the pictures immediately.
If you solicited the photos, or distributed them to someone else, you could face a variety of serious charged under Federal and/or California law.
DO NOT talk to anyone about this case except an attorney, and DO NOT post additional details on , which is a public site that cops and prosecutors can (and do) read.
BEWARE THE PRETEXT PHONE CALL! If you get a phone call from the young person in the photos (or their parents, or anybody else), you should assume the police put him/her up to it, and they're recording the call, hoping you'll make some damaging statements. If you get this kind of call, just say, "I have no idea what you're talking about," and hang up.