HFT in Action?

I was playing around with a new volume study and for grins ran it for the most active stock - Citigroup. A half of a billions shares were traded on Friday. Click on this chart for the full screen view. This is a 1 minutes chart and you can see the price trade between $3.96 - $3.99 after the open. Look at the price action and volume. People talk about HTF and looking at this chart, it makes we wonder how many humans are buying or selling this stock as a swing trade or accumulating. Is it the HFT bots just scalping for tenth a of penny profits between each other to make up this top volume stock?