The complaint already says how: after busting Chronicpain in a CD, he turned over his SR1 moderator/admin account, and then Force used the mod/admin ability to reset passwords & PINs to log into big vendors' accounts and transfer their balance out of SR1 to his own Bitcoin account.

Thanks, I had missed any links to the indictment in the original story, but it's definitely a worthwhile read.

After knowing the background, I don't actually mind the redaction of those details from the evidence in Ulbricht's trial.

Perhaps they pretended to be an extortionist and a hitman in order to convince DPR to send coins to their address in exchange for a "hit" on the "extortionist".