I would be happy to help assist you in understanding your dream. With all this shooting taking place in your dream. It is symbolic of " power" being used between people. This power that is often used are words and actions. Since the dream took place at a family bbq , showing family get together. Sounds like words being exchanged that are hurtful towards others. So perhaps your family has an issue with feuding or disagreeing? With the school library is showing a quiet place of learning. Perhaps the people around you are disrupting your ability to left alone or learn? All around it sounds as though the people around you are using negativity with their words and actions to hurt others.
I hope this helps. If you have anymore questions feel free to ask.