"I just want you to know that we are working on it," Brady recalled the president telling them. "We have to go through a few processes, but under the radar." So said Obama to Sarah Brady on March 30, 2011. Documents obtained by CBS News show that the Bureau of Alcohol Tobacco, Firearms and Explosives (ATF) discussed using their covert operation "Fast and Furious" to argue for controversial new rules about gun sales. In Fast and Furious, ATF secretly encouraged gun dealers to sell to suspected traffickers for Mexican drug cartels to go after the "big fish." But ATF whistleblowers told CBS News and Congress it was a dangerous practice called "gunwalking," and it put thousands of weapons on the street. Many were used in violent crimes in Mexico. Two were found at the murder scene of a U.S. Border Patrol agent. ATF officials didn't intend to publicly disclose their own role in letting Mexican cartels obtain the weapons, but emails show they discussed using the sales, including sales encouraged by ATF, to justify a new gun regulation called "Demand Letter 3". That would require some U.S. gun shops to report the sale of multiple rifles or "long guns." Demand Letter 3 was so named because it would be the third ATF program demanding gun dealers report tracing information. On July 14, 2010 after ATF headquarters in Washington D.C. received an update on Fast and Furious, ATF Field Ops Assistant Director Mark Chait emailed Bill Newell, ATF's Phoenix Special Agent in Charge of Fast and Furious: "Bill - can you see if these guns were all purchased from the same (licensed gun dealer) and at one time. We are looking at anecdotal cases to support a demand letter on long gun multiple sales. Thanks." Any questions? Read more here.