This is arguably the most important part to a Stalking charge.  The one thing you can never count on is how another person will feel or react.  To be charged with Stalking, you don’t even have to know that the other person is in fear – the government only has to say you reasonably should have known.
In other words, you could truly know and never believe what you are doing would cause harm to someone.  But the government may believe “you should have known better”.  Getting charged with Stalking in these cases can be particularly scary when you know in your heart you meant nothing wrong by your actions but were sadly misunderstood.