CarMax slumps after Q2 profit falls

** Shares of used car retailer CarMax KMX.N fall nearly 13% to about $50 premarket

** Co posts Q2 profit of $95.4 million, or 64 cents per share, compared with $133 million, or 85 cents per share, from a year ago

** KMX's Q2 revenue falls 6% to $6.59 billion, compared with Wall Street estimates of $7.02 billion - data compiled by LSEG

** As of last close, stock had fallen 30% YTD