 Within 15 minutes, Cells 1 and 2 had secured the communications site.Signaled by the explosion of Cell 1's RPG-7 round, Cell 3 immediately attacked the TACAN installation by firing one of their own RPG-7s, which destroyed the electric generators.Upon hearing the noise of explosions, the on-duty US technicians rushed out the front door of their operations building where they were met by PAVN gunfire.