College is an interesting time in your life where you should feel you can be whoever you want to be. There is no need for confidence problems. There are always going to be those which judge you superficially, take it like a grain of salt, and know that they will run into their own problems due to that way of viewing others. Don't be upset when you run into these other people, you can easily give the "whatever" approach to them as they aren't deserving of your time.
As for getting angry and causing damage, its up to you to remain in control and not let your anger get the best of you, as you are always in control of your actions. Always remember that. Even in moments of rage, to do something or not, is still an option. Always think about the next action, before acting.
As for killing the other happy people you see around you, there is no need for that, as it would not help anybody, including your own happiness. Death never brings happiness to anybody and you don't know those other people who go through their own daily struggles. Everybody has their own way to relax, to enjoy themselves and get away from their own stresses and/or sadness. Just because they appear happy in your eyes, doesn't mean they are living the happiest of lives. Everybody struggles, and its up to you to choose how you want to deal with your sadness and moments of happiness (which I'm sure everybody wishes they had more of on a daily basis).
Just as "Isabel" said, a professional may be able to help you out as I believe communication and venting out your frustrations may help you see you have more options on how to deal with these situations than you may realize.
Ask at your University's Information area if they have a psychologist for students just to "talk to", and see where it goes from there.