You're not a bad person, and you weren't as a child either. An 8 year old, in my opinion, can't be a bad person. She can do bad things, but that reflects on her surroundings. If children act out or do something they're not allowed to, so many adults see them as "difficult", but the truth is that they are in aa difficult situation. You can't punish or yell a child out of a difficult situation. Punishment will only make the child trust adults even less than before, and you have a bad spiral going.

When that teacher heard you talking about those things, he or she should have talked to you about it, asking you about why you came up with that, if you heard or saw anything scary on tv or otherwise, how things were at home etc. And, calling your parents, she or he should have told that she was worried, not that you were bad. And your parents should have done the same. It's never ever the child's fault. A child can't be bad. There's nothing for you to be ashamed of. That shame was put on you, but it isn't and never was yours to carry. What your parents did to you, how they treated you, was not ok. If you had been a litte different, they might have turned you into a criminal. They. Many kids end up that way because of how they are treated by their parents and other adults in their lives. Luckily you didn't. And you're all the better person for going through all of that and still turn into such a good person now.