Abnormal behavior before the market close

Last Friday (May 29,2009), before the market close, the volume surged and price climbed up as well. See the NASDAQ 15 m chart below[1] . In the last 15 minutes, the volume surged to 400M, skyrocketing !

What does this abnormal behavior before the market close mean ? Usually, it is a bullish sign, especially for stocks. Let's watch and learn.


[1] chart