You don't really want to hurt anyone, I know, and as you say, you need help fast. If you have a family doctor, please call him or her right away. If you don't have one, is there a crisis hotline in your town, like an emergency phone number for people who need to talk to somebody really soon?
If not, you can get help the next time you have these feelings by going to the emergency room of your hospital. Just tell them what's going on.
You say person following you everywhere? Is this someone that you know or someone no one else sees? Or is it a voice? If it is not a real person you need to speak to your psychiatrist ASAP. If you do not have a psychiatrist presently then you should try to find hwo to get one, such as if you need to see your primary doctor first, etc. This sounds pretty serious and not something you should try to handle on your own.