If a crowd turns violent, effectively becoming a "mob," it may execute physical attacks on people and property, such as by throwing homemade weapons like molotov cocktails, firing small arms, and planting improvised explosive devices.[1] If the violence is not pre-arranged, a crowd may resort to throwing rocks, bricks, bottles, etc. If violence is pre-arranged, the crowd can hide their weapons, or vandalism tools, well before the crowd formation, catching law enforcement by surprise.[1]