そのときに歴史の先生がこう呟きながら連れて行かれます。
Source: https://www.youtube.com/watch?v=3xs-XWk_oQA 1:17
I'm assuming it's the word 斯う meaning "in this way," and here it would be describing how the teacher said the quote to follow. Is this こう anything like the quotative like in English that can be used for either literal quotes or paraphrasing? For example, "He was like, 'When is history not essential?'"