User blog comment:Xilinoc/Ch. 543 - Letters/@comment-8669536-20130626135749/@comment-2211792-20130626155918

@ColJazzman >>Also that Quincy with the beard who was watching I don't think he is in the Stern Ritter team, but I do believe he has a letter like Quilge who was in a different group.

That guy was the one who mind-controlled Jidanbo (see chapter 500, you can see someone "gehgehgehing" as Jidanbo smashes the building). Since only Stern Ritters participated in the invasion, the "onlooker" has to be one, too.