A USA TODAY review finds thousands of guns were sold to people who should have failed their background checks. Now, federal agents have the dangerous jobs of trying to get those guns back. USA TODAY

WASHINGTON— Federal authorities sought to take back guns from thousands of people the background check system should have blocked from buying weapons because they had criminal records, mental health issues or other problems that would disqualify them.

A USA TODAY review found that the FBI issued more than 4,000 requests last year for agents from the Bureau of Alcohol Tobacco Firearms and Explosives to retrieve guns from prohibited buyers.

It’s the largest number of such retrieval requests in 10 years, according to FBI records – an especially striking statistic after revelations that a breakdown in the background check system allowed a troubled Air Force veteran to buy a rifle later used to kill 26 worshipers at a Texas church last month.

The FBI’s National Instant Criminal Background Check System (NICS) vets millions of gun purchase transactions every year. But the thousands of gun seizure requests highlight persistent problems in a system where analysts must complete background checks within three days of the proposed purchase. If the background check is not complete within the 72-hour time limit, federal law allows the sale to go forward. ATF agents are asked to take back the guns if the FBI later finds these sales should have been denied.

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In addition to the public safety risks, the ATF agents tasked with retrievingthe banned weapons from unauthorized gun owners across the country are exposed to potentially dangerous confrontations.

“These are people who shouldn’t have weapons in the first place, and it just takes one to do something that could have tragic consequences,” said David Chipman, a former ATF official who helped oversee the firearm retrieval program. “You don’t want ATF to stand for ‘after the fact.'”

It was not immediately clear how many gun seizure requests agents successfully executed last year or how many weapons were ultimately recovered. Since multiple firearms can be purchased in a single transaction, the actual number of guns that should have been banned could be even higher.

Chipman, now a senior policy adviser for the Giffords Law Center which advocates for more gun restrictions, called the retrieval process “uniquely dangerous.”

Stephen Morris, a former assistant FBI director, said FBI examiners who review gun purchasers’ backgrounds also recognize the risks.

“They are very aware of the inherent risk to law enforcement officers when they (seek) a firearm retrieval,” said Morris, who recently oversaw the bureau’s background check operation based in West Virginia. “They feel tremendous pressure to make a determination” within the three-day period.

Review of the gun vetting system

The sudden spike in gun retrieval…