According to Anna Williams, Abby's Mom, she said the girls saw a gun, spoke of a gun and a gun was heard being cocked in the audio. So I don't think it was a hey guys, the person you cane to meet is down the hill. It was an abduction. AJMO
Start at 49 min mark, gun at 51:00 min mark
The girls are discussing which way to go. It appears they were talking about two ways to go but said it was hard to hear the audio.
Abby says "Is that a gun? He's got a gun."
BG says "Hey" (probably supposed to be "Guys")
Libby then says "Hmmm"
BG says "Down the hill" and then the sound of a gun cocking is heard