A bombshell report released Wednesday on Operation Fast and Furious faulted a range of federal agencies for the failed anti-gunrunning program and accused officials in charge of a "disregard" for public safety. In the wake of the report, one Justice Department official resigned and another retired.

The sprawling report by the department's inspector general is the most comprehensive account yet on the deadly operation which allowed weapons to "walk" across the U.S.-Mexico border and resulted in hundreds of firearms turning up at crime scenes in both countries.

The report says Attorney General Eric Holder was not made aware of potential flaws in the program until February of last year. But the report cites 14 other department employees -- including Criminal Division head Lanny Breuer -- for potential wrongdoing, recommending the department consider disciplinary action against them.

One congressional source told Fox News the report was "more brutal than was expected."

The report marked Jason Weinstein, the deputy assistant attorney general for the Criminal Division, as the highest-ranking DOJ employee in a position to stop the program. Weinstein, who disputes the findings, is resigning in the wake of the report.

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Another official criticized for not asking enough questions about the Furious operation, former ATF acting director Kenneth Melson, retired after the report came down.

The nearly 500-page report was completed after investigators reviewed 100,000 documents and interviewed 130 people.

The report slams both the Phoenix office of the Bureau of Alcohol, Tobacco, Firearms and Explosives and the U.S. Attorney's Office for not taking action. The program caught the attention of Congress and the rest of the country after weapons from Fast and Furious were found at the crime scene of murdered Border Patrol agent Brian Terry.

"Indeed, no one responsible for the case at either ATF Phoenix Field Division or the U.S. Attorney's Office in Arizona raised a serious question or concern about the government not taking earlier measures to disrupt a trafficking operation that continued to purchase firearms with impunity for many months," the report said. "Similarly, we did not find persuasive evidence that any supervisor in Phoenix, at either the U.S. Attorney's Office or ATF, raised serious questions or concerns about the risk to public safety posed by the continuing firearms purchases or by the delay in arresting individuals who were engaging in the trafficking.

"This failure reflected a significant lack of oversight and urgency by both ATF and the U.S. Attorney's Office in Phoenix, and a disregard by both for the safety of individuals in the United States and Mexico," the report said.

The office said it "identified serious failures" by ATF leaders in supervising the operation.

The report faults both Breuer and Weinstein for not notifying superiors about a prior Bush-era program called Wide Receiver when questions about Fast and Furious arose. The report also said Weinstein knew about Fast and Furious from discussions with an ATF official in early 2010 and his review of wiretaps that year.

Weinstein told Fox News that he's resigning so as to not "distract" from the department's work. But he took issue with the report's conclusions about him.

The inspector general's report cites a conversation Weinstein had with ATF official Bill McMahon in April 2010. At the time, the department was trying to bring indictments in the Wide Receiver investigation. Weinstein said he was so upset to learn that ATF walked guns that he met with McMahon and others. After the meeting, McMahon told Weinstein about another operation, describing it to McMahon as "the opposite of Wide Receiver" and insisting it didn't involve gun-walking, according to Weinstein. That was Fast and Furious.

Months later, according to Weinstein, McMahon told Weinstein that some ATF officials in Phoenix felt wiretap applications were moving too slowly and the delay was having an effect on the investigation, so Weinstein helped push that along. Weinstein says he only read the cover sheets of wiretap applications. But the IG report says Weinstein was in a position to stop the program.

The report by Inspector General Michael Horowitz found the ATF and U.S. Attorney's Office in Arizona shared equal responsibility for the gun-walking programs. It also said senior leaders did little immediately after Terry's death to inquire about Operation Fast and Furious. It faulted ATF headquarters for insufficient oversight of the program. And it cited the "inappropriate" effort to encourage dealers to sell firearms in transactions they knew were unlawful for weapons they did not intend to seize.

Further, the report said that an erroneous claim in a February letter to Congress that the department did not knowingly let guns walk was the result of officials relying on inaccurate information in the letter-drafting process.

DOJ officials Monty Wilkinson and Gary Grindler were also criticized for failing to inform Holder that two guns connected to Fast and Furious were found at the Terry murder scene.

House Oversight and Government Reform Committee Chairman Darrell Issa, R-Calif., who along with Sen. Charles Grassley led the charge on Capitol Hill to investigate the operation, said Wednesday that the report "confirms" congressional findings "of a near total disregard for public safety" in the program.

"Contrary to the denials of the Attorney General and his political defenders in Congress, the investigation found that information in wiretap applications approved by senior Justice Department officials in Washington did contain red flags showing reckless tactics and faults Attorney General Eric Holder's inner circle for their conduct," he said.

In an interview with Bret Baier on 'Special Report' Wednesday, Issa said that the report was good overall, but questions remain about a cover-up.

"The Terry family wants the answer for the initial failure and for the cover-up," he said. "[Today's resignation] is only the tip of the iceberg. [Weinstein] should have been gone a year and a half ago and only resigned when the report pointed at him specifically."

Issa told Fox News that there is "no question" that there needs to be "real reform" in the Justice Department.

"We owe it to the Terry family to fix the system," he said. "We don't know, or will never know, why such a reckless or foolish tactic was done, continued and covered up."

Issa called on Obama to "provide accountability" for those "who failed to do their jobs."

Issa's committee counterpart, though, said the report proved that Holder and other senior department officials did not green-light the program.

"The IG's comprehensive report debunks many of the extreme allegations made by Republicans and confirms many of the conclusions reached in a report I issued nearly a year ago - that neither the Attorney General nor senior DOJ officials authorized or approved of gunwalking in Fast and Furious, that gunwalking started under the Bush Administration in 2006, and that ATF agents in Phoenix and the U.S. Attorney's Office in Arizona share responsibility for misguided operations spanning five years," Rep. Elijah Cummings, D-Md., said.

B. Todd Jones, acting ATF director, said in a statement that the report was "rightfully critical" of ATF's handling of Wide Receiver and Fast and Furious.

"ATF accepts full responsibility for its failure to exercise proper leadership and oversight of these investigations. Combined with the lack of effective and accurate internal communication up and down the chain of command, our shortcomings led to a series of regrettable events," he said. Jones said the findings were referred to an internal office to determine whether "adverse actions" are warranted.

The inspector general is expected to testify on the findings on Capitol Hill Thursday morning.

Click to read the Fast and Furious report.

Fox News' Mike Levine contributed to this report.