Violent tantrums at 6 and a 1/2. Seeking advice.

Hey y'all, I've never dealt with a kid before who did this. It feels totally strange to see it in a kid who's already nearly 7. I don't get it and I don't know how to help her change her behavior. Maybe you have ideas?Sometimes when she gets angry, she starts grabbing shit that's up high and hurling it at the ground, or she'll run off and find something and destroy it. Sometimes she'll come and find us first and gravely state something like, "I'm going to stab my tablet with a knife."AND THEN SHE'LL ACTUALLY GO AND DO IT.When she starts with these behaviors (often triggered by one or more people deciding to do something without her), we warn her about natural consequences, offer her alternative behaviors for getting attention or expressing anger, try to help her understand her feelings and cope with them, try to get her to have a snack, and when all else fails, we end up having to restrain her.Often, when restrained, she'll intentionally try to physically harm the person restraining her, and she's gotten big enough that sometimes she succeeds (and then continues to try, despite warnings that she's hurting someone she typically cares about). Now when we can't safely restrain her, she gets locked in her room until she stops trying to hurt people and we can safely engage with her again.When she was locked in her room this morning, she threatened to destroy the heat vent.No one in our house has ever behaved this way, and I can't imagine she's emulating anything from any of the TV shows she occasionally watches.Usually she's such a fun and reasonable kid, but she's gotten so mean lately. She also started first grade this year (after having stayed home from Kindergarten last year) and then ran away from school one day (despite claiming that she likes her school) and got dropped off at home by a stranger.It seems like she's trying really hard to get our attention, but she denies that that's what's going on, and rejects our attention when we offer it. We're exhausted.Can anybody give me a fresh perspective or some of that sweet, sweet advice-juice? via /r/Parenting https://ift.tt/2BjQFNz