The Turf Club was a gambling establishment in Las Vegas, Nevada. A shady man named Uncle Lou stood outside, waiting for targets that he felt he could con. He had a briefcase with a large sum of money in the trunk of his car, presumably taken from the people who fell for his con act.
Biff was repeatedly trying to get his grandmother, Gertrude Tannen, to bet for him at the Turf Club since he was underage. He gave her a twenty dollar bill that he stole from a table to his grandmother to bet at the Turf Club on the Chicago Bears. She didn't bet on the Bears, and they lost against the Los Angeles Rams, making Biff twenty dollars poorer. Biff told her to make another bet, on the Washington Redskins. However, when they beat the San Francisco 49ers, she only gave Biff back his twenty dollars, and kept the rest for herself. When Gertrude claimed Biff was as greedy as his father, Biff stated that he learned that from her.
Lou noticed the altercation, and noticed that Biff used a book to select the winners. He wanted to get a look at Biff's methods himself. He told Biff that they could earn money together, as he would be able to make the bets while Biff could not. Biff reluctantly agreed when Lou told him to wait for him in the parking lot. While Biff was waiting, Lou killed Gertrude, and put her in the back of his car to bury her. He told Biff that he had talked to his grandmother and said that she was still playing the slot machines.
Lou stole the Grays Sports Almanac from Biff, and when he realized that it was the book that stated the winners, and not any methods that Biff had employed himself, he planned to kill Biff and bury him next to his grandmother. However, when he went to hit Biff with a tire iron, Biff caught it and killed him instead.
Biff justified the murder in his mind based on the fact that Lou had killed his grandmother. He buried Lou, and took all the money that was in his briefcase. With the money, he covered up the murder of Gertrude by paying to have a death certificate forged that stated she died of natural causes.