Most of the humans we fought wore blood red bandanas. I seem to recall hearing of a criminal organization operating in the Eastern Kingdoms known as 'The Defias Brotherhood' who are known for their red masks. Why they are active here in Kalimdor I don't know, but kill any that cross your path and bring their masks to Eitrigg in Orgrimmar. He'll be able to determine if these are in fact Defias masks.
Reputation