In a 471-page report, Inspector General Michael Horowitz said it was the agency's misguided strategies, errors in judgment and management failures that led to the bungled gun-trafficking probe in Arizona that resulted in hundreds of weapons turning up at crime scenes in the U.S. and Mexico.
Horowitz referred over a dozen people for possible disciplinary action for their roles. The report did not criticize Attorney General Eric Holder.
In response to the review, Deputy Assistant Attorney General Jason Weinstein resigned, and former ATF director Ken Melson retired from the Justice Department, effective Wednesday.
The report found no evidence that Holder was informed about the operation before Jan. 31, 2011, or that the attorney general was told about the controversial gun-walking tactic employed by the department's Bureau of Alcohol, Tobacco, Firearms and Explosives.
The Associated Press contributed to this report.