They are scary! I know one time a thought like that came from nowhere inside of me! It certainly wasn't my thinking and I certainly didn't entertain it, but it freaked me out enough to mention it to t and he said something about "unwanted thoughts". They can happen, and do. It's when we latch onto these unwanted thoughts and entertain them, begin planning, feeling good about them, etc., that they can be a big worry.
I would certainly go to someone just for a bit to talk though, if you feel you even want to
be safe,
kd