Put this clip at the exact frame your rescuer appears, then follow it with the Enemy Spotted cue if opponents react, or lead into it with the FBI Open Up cue for a raid-style entrance that escalates in two steps.
关于此声音
This clip is the sharp metallic pump and lock of a shotgun being readied, lasting under a second with no voice at all. It feels tense and threatening at the same time as reassuring, like armed help has just stepped into the room. It comes from the Half-Life games, where that readying noise heralds an ally arriving armed.