Recent high-profile mass shootings that resulted in massive casualties and property loss have garnered public attention and interest in solutions. As such events increase in frequency around the world, they continue to baffle public officials and the media who often portray them as the governments’ failure in forewarning; yet no tightened social stability policy nor weapon control is seen at the moment. This project aims to prevent mass shootings by identifying weapons and suspicious personnel in the crowd through patrol drones. Embedded with a camera, a wireless charging pad, and a Raspberry Pi board, patrol drone will fly through the pre-planned waypoints, and provide real-time weapon detection with high accuracy at low cost. It will report all suspicious targets and find a charging station automatically when needed. Manual intervention could be kept to a minimum. Our team finds a huge market potential in the wide application of patrol drones, such as meteorological research, real-time air quality monitoring, crowd control. This project will prove that patrol drone is possible, and expect an advent of its widespread usage.