If one look at the one minute chart.
One can see that this is a classic day trader's test pattern. Probably done with the help of a computer algorithm to execute this fast. A test is a buy at market and subsequent equal sell at market of the same amount of shares that's larger than what the market can handle in order to see if the support/resistance will fall through. The trader pays a little premium to find out the resilience of the current trend.
Why is this obvious? Use a low pass filter on the stock volume and substract the high frequency with the coefficient of the low pass filter and you will see that the 1st minute buy is approximately equal to the extra volume of the next 4 minutes.