From the article: "I was specifically told by several BP agents that it is the sound of a flashlight hitting a head," Heyman said in a separate email. "I was never told either of those acromyms (or any others). I suspect that those are after-the-fact rationalizations of a disturbing word, but I cannot prove that (I do not directly have evidence). What I do have evidence of is that is was described to me by agents as the sound of a flashlght blow to the head."
This is it, but with a 'K' unless the AZ sector guys use alt spelling.