Systems and methods are disclosed for reliably detecting gunfire in enclosed spaces having significant acoustic reverberation. Implementations are configured to quickly and reliably report the room or portion of a room where gunfire is located. Innovations herein may ensure low false alarm rate by thresholding, pattern recognition and/or detecting the muzzle optical flash. In some embodiments, a review center with trained personnel may evaluate the incident before reporting to local authorities. The indoor system can be incorporated into an outdoor gunshot location system to better protect a local area such as a campus or a transportation hub. Systems and methods herein may involve features and functionality associated with additional resources, such as intercoms, cellphones, and access control, to provide mitigation of harm in case of a shooting.