Yep you just have to kill him and either rest for 24 hours or kill off all the brotherhood in the studio and around it, or they will kill you
- edit with a non violent method:
Instead of the above simply reverse pickpocket, instead of taking a item from a npc you give them one, a power helmet to Three dog and go through a door. Reenter said door and go to Three Dog and he will be wearing the power helmet, then you can steal his head wrap and glasses.
Ah and save before you attack each pickpocketing.