anything from the kiosk, why would you think it's OK to lean on it? You were asked to move three times before they threatened to call security. For all they know, you are just waiting for a prime moment to smash a case and grab merchandise or to hold them up. This is entirely on you. I would have been nervous if you were not a customer but leaning on my kiosk asked repeated requests for you to walk away. Would it have been so difficult to hang out in the store where you son was conducting business, or the bench that is designed for people to sit on?
Employees don't need to be fired. You weren't being a customer at that time, you were just loitering. It's also worth remembering that lots of folk have CCW permits. Suspicious behavior can make people a little trigger happy.