2000 honda cr250r running full RPM?

I have a 2000 honda cr250r, one day i went to start it and it started up idling what sounded like full RPM, it was screaming like crazy, kill switch wouldnt kill it, managed to put it in gear and drop the clutch to shut it off. Started it a few days later and it was fine, then just the other day i was riding and hit a small jump, when i landed the bike took off and i fell off the back, it drove on its own for a good 30-50ft until it fell over, but while it was leaning on its side it was idling at the full RPM again, and couldnt get it shut off with the kill switch. Went to start it a few minutes later and same thing happened with the bike screaming at crazy high rpm, my buddy did a few adjustments to it and it seemed okay enough to drive it back to the truck and bring it into the shop, my reed boot needs to be replaced because of split in the rubber, but i can't figure out why this would have happened, and want to find a solution because its scary as hell when it happens and is dangerous

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