Large-scale security screening in public areas, including airports, stations, large events, is becoming increasingly important. Multi-modal sensors in screening systems provide enhanced security features, including tracking, identification, and improved resolution, among others. The goal of this project is to advance the development of a prototype of a security sensor that combines an optical camera, a depth sensor and a radar. In the long term, the vision of this project is the development of a seamless security checkpoint, in which humans would not need to stop and be screened but can walk freely. MERL has an early hardware prototype combining an FMCW mmWave radar and a depth camera, with an early version of the processing steps. The project goal is to fully develop the processing pipeline, the user interface, and some processing techniques necessary for the project. MERL will provide the hardware prototype to the team.