It has to be him (judging by the amount of BTC in there, I'm pretty sure this is the case), otherwise that means his wallet is compromised.
I really wonder:
1. Who is Darkstar? How did the collaboration between him and Chipmixer happen? Why did Chipmixer chose him instead of other famous signature campaign managers? As I see, he has rarely managed sig campaigns.
2. Why did he disappear after the Chipmixer incident? Is he afraid that he may get caught?
By the way, what happened to Chipmixer owner, is he arrested or is he in the list of most wanted people?