I finished getting the fragment from Dustman's cairn returned to Jorrvaskr. Upon entering instead of being asked to follow someone to Skjor and the circle I get attacked by Athis. I dispatch him and head out the back door where I get attacked by more companions. I rush back into the house and 2 of them follow along with Farkas. Farkas and I kill them. One was Ria can't remember the other. After they are dead I went back outside and joined the circle and the quest went on normally.

My question. Is this a bug or were they suppose to attack me and Farkas.

That's a bug. It is most likely caused by having a bounty in one or more holds. Those NPCs you killed are "supposed" to be your friends.