This is an inexpensive detector to prevent mass murders by guns, and illegal use of fire arms. Inexpensive antenna bands affixed to ammunition casings or to the barrel or other part of a fire arm activates a detector/sender which is generating specific radio frequencies, and which is also a beam-forming generator.The beam of a specific radio frequency is reflected back to the detector, mounted on a building, or carried by a law enforcer. When the reflected signal from the antenna bands reaches the detector, an output signal is produced in the detector, which is used to alert safety personnel or electronic alarms, that a gun is nearby. It also has several safety features in case the antenna bands are tampered with, or removed.