 One cooperating dealer expressed his concerns in a series of emails in April and June 2010 to GS David Voth, who assured the dealer that ATF was monitoring the suspects using a variety of techniques that he could not discuss in detail.The tactic of letting guns walk, rather than interdicting them and arresting the buyers, led to controversy within the ATF.As the case continued, several members of Group VII, including John Dodson and Olindo Casa, became increasingly upset at the tactic of allowing guns to walk.