You move the market by buying in a favored account, and selling to each of your accounts by placing asks at a higher price than the original price moving the market up and making profits in the 61 accounts he had. This is a known issue for brokers, but I'd never seen a non-professional able to do this.
More info on trade dates and methods here: http://www.sec.gov/litigation/complaints/2011/comp22142.pdf