The man had been infected with tainted water from The Orchid and brainwashed by a subaudible frequency from the Mueller device over Sovogda, Russia, all part of Elena Derevko's plan to enact Rambaldi's "endgame." When the APO team met up with Brodien, the last surviving member of a DSR team that had been sent into Sovogda, they attempted to go down into the subway system to reach the epicentre of the Mueller device in an effort to stop it.
As Brodien opened the gate to the subway, the Infected Russian stabbed him through the fence. He then pulled the door open and looked towards Sydney and Nadia. As he came for them, they shot him dead. Brodien died moments later.