Grossman was a thief and an associate of Bela Talbot.
Grossman and his buddy Wayne are hired by Bela Talbot to steal the Curse Box containing the Rabbit's Foot from John's lock-up. Wayne is shot when he trips a booby trap John has rigged in the lock-up. His luck changes after he touches the Rabbit's Foot: his neighbor is an ex-Army medic who can tend his wound, and he wins at cards. Sam and Dean track them from the lock-up and take the foot from Wayne, his luck changes, and he is killed when he slips on a bottle and is impaled on a BBQ fork.
The Winchesters later return to interrogate Grossman about who hired them to steal the Rabbit's Foot and he gives them Bela's alias - "Bela Lugosi".