This is from Business Insider but it is based on a WSJ Report so I will use the original source. This just gets worse every time some new piece of the puzzles is revealed.
Federal authorities are probing why the U.S. in 2010 let go an Arizona man accused of supplying grenades to a Mexican drug cartel, a case that played a role in the ouster last week of the nation’s top firearms regulator and the U.S. attorney in Phoenix.
U.S. officials said missteps in the case, which hasn’t been previously disclosed, are being investigated by the Justice Department and Congress. Federal agents in 2009-10 at the Phoenix office of the Bureau of Alcohol, Tobacco, Firearms and Explosives led the case against the suspect, who they believed was dealing grenades to cartels in Mexico. The case was overseen by prosecutors in the Arizona U.S. attorney’s office, the U.S. officials said.
The Arizona U.S. attorney’s office and the Phoenix ATF office are the Justice Department units behind another botched operation, called Fast and Furious, which has been the subject of intense congressional interest this year. The Fast and Furious program allowed suspected smugglers to buy about 2,000 firearms, some of which later turned up at drug-related crime scenes in Mexico and the U.S.
Many bloggers have posted on this earlier, including myself. Maybe some of them knew how very deep it would go but I have seen no indication anyone realized it went as deep as explosives and grenades and made the connection to this man.
[…] ATF agents arrested Mr. Kingery in Arizona in June 2010 after months of surveillance and seized 116 grenade hulls and parts in his possession, the officials said.
The suspect told investigators he helped operate a mill in Mexico manufacturing improvised explosive devices made from the U.S.-sourced grenade components, they said. Mr. Kingery allegedly said he supplied the weapons to a cartel called La Familia Michoacana and also helped the cartel convert semiautomatic rifles into military-style machine guns.
Nonetheless, he walked free without being charged after just hours in custody, officials said.
That decision is at the crux of a bitter fight between ATF agents and prosecutors at the U.S. attorney’s office in Phoenix. The lead ATF agent on the grenades case, Peter Forcelli, “was horrified with the thought of releasing this individual” and “practically begged” senior prosecutor Emory Hurley “for permission to arrest the suspect on a criminal complaint,” according to an Aug. 31 letter sent to a congressional committee on Mr. Forcelli’s behalf by an attorney with the Federal Law Enforcement Officers Association, a group that provides legal assistance to law enforcement officers.