What you probably witnessed was a mild short squeeze, that day with over 4.5 million shares looked like one to me. The S/P peaked and settled down once it was determined nothing for the shorts to be worried about was released. The last few days on the TSX weren't really good and todays big drop is representative of that. I'm no expert but when I see big price swings in both directions it appears that shorts are usually trying to cover or daytraders are more active.