It's part of the quest, "Andy and Charlie". Andy, a retired ranger who is living in Novac, has tried contacting Ranger Station Charlie, but hasn’t been successful and is worried. The player character can suggest checking up on his friends and at first Andy hesitates. However, at the end of the conversation, he changes his mind.
Upon entering the station there are bodies of Rangers everywhere, and the office has been boobytrapped. Disarm the traps and search the dead Rangers. There are 2 holotapes explaining what occurred. Return to Ranger Andy and tell him the bad news.