I ran away from the person from my past, will my friends suspect something?

You may not want to confide in these people if you don't know them very well; but what you could say is simply that you saw someone from your past that you had an upsetting experience with and your emotions came flooding back and you just got very upset. They won't suspect that it was a person who d you. Just tell them that this person reminded you of a very upsetting time in your life and you just felt very upset. They'll understand. If they do not then they don't need to be your friend. I also urge you to speak to someone about this so it doesn't destroy you emotionally. Believe me, it will.