WASHINGTON — Knowledge of Operation Fast and Furious, a controversial border security strategy that allowed guns to be shipped illegally into Mexico in an effort to track them to drug cartels, went to the top of the Bureau of Alcohol, Tobacco and Firearms, according to evidence released on Wednesday at a House Oversight Committee hearing. Witnesses at the House hearing included three relatives of a Border Patrol agent killed in Arizona and three A.T.F. agents, right. The operation, which began in 2009, came under fire after two guns linked to it were found at the scene of the killing of...