He and two members of his gang are encountered in Highland Park, right after the arrival. Adam Jensen can ask him about the area, and buy a couple of items. He'll say that the area is currently occupied by unknown Spec Ops soldiers, later revealed to be part of Belltower Associates.
By 2029, he has either been killed or replaced by a new leader named "Magnet".
He is never named in the game. The interaction window identifies him simply as MCB Gang Leader.
His brother was another MCB named "Big Rizzle", who was killed by Belltower Spec Ops for moving into the area near their FEMA facility. Picture's of Big Rizzle's murder can be found on Officer Jenny Alexander's office wall.
The MCB Gang Leader and Grayson are the only arms dealers that do not wear brooches on their chest.
He is the only merchant in the game who does not use a computer for trading. Instead, the trading action resembles one found in the original Deus Ex game.
Jensen can simply kill or knockout the dealer and his two bodyguards and loot their corpses for their wares.