Washington ( CNN ) -- Firings and charges against Justice Department officials who oversaw the agency 's flawed gun-running operation are likely to come in the next six months , Attorney General Eric Holder said Thursday . Holder was speaking before the House Oversight and Government Reform Committee on the controversial sting operation called Operation Fast and Furious . Asked what steps he had taken since the controversy came to light 13 months ago , Holder said he is awaiting the conclusions of an internal investigation . Regarding people found culpable in that inquiry , he said , `` I can assure you those people will be removed from federal service . '' Any possible charges will not be filed until the department has the evidence to get a conviction , he said at the hearing . The operation , designed to monitor the flow of weapons , allowed illegally purchased firearms to be taken from U.S. gun stores across the Mexican border to drug cartels . However , hundreds of weapons were lost or unaccounted for , and a storm of outrage erupted when two of the missing weapons were found at a site where Border Patrol agent Brian Terry was killed in December 2010 . Terry 's family filed a $ 25 million wrongful death claim Wednesday against the federal government , charging that U.S. investigators allowed murder weapons into the hands of criminals . `` The murder of Agent Terry and other acts of violent crimes were the natural consequence of ( the ) decision to let dangerous weapons designed to kill human beings 'walk ' into the hands of violent drug-trafficking gangs , '' the claim said . Democrats and Republicans have been at odds over who knew what about the operation and when . At the outset of the hearing , new information on the operation was scarce , and the back-and-forth between members of the two parties dominated . Rep. Darrell Issa , R-California , threatened to begin a contempt proceeding against Holder to force him to release more documents and pressed him for proof that such gun-running will not happen again . Republicans are investigating how high up the operation was sanctioned , while Democrats defended Holder 's testimony that he did not know about it . The showdown comes after Issa and the Justice Department exchanged sharp letters in recent days . The Justice Department sent a pointed letter to Issa late Wednesday , rejecting his demand on Tuesday that certain documents be turned over by next week . In his letter to Holder , Issa blasted the Justice Department for dumping -- after the close of business Friday -- important , long-sought documents that disclosed that Assistant Attorney General Lanny Breuer had discussed with Mexican officials a plan to allow illegal guns `` to walk '' into Mexico , where Mexican officials would arrest the gun-runners . Issa said an e-mail showed that `` Breuer suggested allowing straw purchasers cross in Mexico so ( Mexican authorities ) can arrest , prosecute and convict . '' `` These new documents show that Breuer made this statement on February 4 , 2011 , the same day Assistant Attorney General Ronald Weich wrote to Congress denying that the department allowed guns to walk , '' Issa said . The Justice Department fired back Wednesday , claiming that Issa 's letter showed `` significant misunderstanding both of the documents we recently produced and of the Department 's position on the issues you raise . '' The five-page letter signed by Deputy Attorney General James Cole strongly rejected the claim that the documents show that Breuer supported letting illegal guns make their way to Mexican cartels . `` Assistant Attorney General Breuer proposed to his Mexican counterparts a scenario in which those carrying illegal weapons across the border would be arrested at the border by Mexican officials and charged in Mexico . While these officials ultimately did not pursue that strategy , it is neither fair nor accurate to say that this was advocacy of 'gunwalking ' . It was not . '' Republicans have pressed to learn whether top Obama administration officials were aware of the controversial tactics , but to date , Breuer is the highest-ranking official shown to have any awareness of any possible gun-running operation . Democrats have released documents suggesting that the U.S. attorney 's office in Phoenix and the Bureau of Alcohol , Tobacco , Firearms and Explosives field office in Phoenix were at the heart of the decision-making in developing sting operations , including Operation Fast and Furious . Issa said in his letter to Holder that , `` if the department continues to obstruct the congressional inquiry by not providing documents and information , this committee will have no alternative but to move forward with proceedings to hold you in contempt of Congress . '' The Justice Department response Wednesday rejected Issa 's February 9 deadline to produce all demanded documents . Cole called the deadline `` impossible '' to meet because of the broad scope of the request . He did not directly refer to the threat of a contempt charge by Issa .
NEW : Slain agent 's family filed a $ 25 million wrongful death claim . Attorney General Darrell Issa says consequences for the operation are near . Democrats Rep. Eric Holder is demanding documents from the House Oversight and Government Reform Committee . Issa has threatened Holder with contempt if a deadline for the documents is not met .