Do you know who the person behind the mask was? At the end of ';Criminal Minds'; season finale last night.?

Not too long ago, the team was on a case in Boston that was related to the first case Hotch ever worked in the BAU. Back in the day when Hotch was still wet behind the ears, the case was of a serial killer who had one surviving victim (played by C. Thomas Howell). In Boston, he learned that the lead cop on the case had taken a deal from the killer....they stop hunting him, and he'd stop hunting victims. The cop and the killer had their deal, but it expired when the cop died. He went back to killing. At one point in the episode he blitzed Morgan and took his credentials. He offered Hotch the same deal he'd offered the cop....Hotch said he doesn't make deals. They caught the guy (who turned out to be the person they thought was the single survivor), but in the end he chewed his wrist open and escaped. This is the guy in Hotch's apartment tonight. This is the deal he was talking about.Do you know who the person behind the mask was? At the end of ';Criminal Minds'; season finale last night.?
I can't remember the name of the character, but I think it was the guy that made a deal with a former detective. The BAU took the case because it was one of the first';Hodge'; worked on and the lead detective asked him to come look at the case again. In the earlier case the detective asked Hodge to leave because he made a deal with the killer then the killing stopped for a little while. I am sorry if this doesn't make any sense but I am not sure how to explain it.