More than 75 percent of the people who received gun license revocations last year in Illinois ignored the notices, Illinois State Police said.

State police issued a report late Thursday in response to questions about the gunman who fatally shot five co-workers at a suburban Chicago warehouse last week. The man, Gary Martin, used a gun in the Aurora attack that he never should have been allowed to have because his firearm-owners card was revoked in 2014.

Martin died in a shootout with police shortly after he opened fire.

"The only way we can honor those who died — the only way we will ever be safer — is to shine the brightest light on the good, bad, and ugly of this system and to lay bare for the public and policy makers the depth and breadth of our vulnerabilities," ISP Acting Director Brendan F. Kelly said in the report.

State police say their records show that about 10,800 firearm-owner cards were revoked in 2018 but that only about 2,600 of those individuals returned notices. Revoked card holders are supposed to return the notices, or firearm disposition records, which document individuals receiving transferred firearms from revoked cardholders.

In Martin's case, he was prohibited under Illinois law from having an owner's permit or owning a gun because he was a felon in Mississippi where he was convicted of aggravated assault in 1995. But authorities say Martin passed two background checks before buying the Smith & Wesson .40-caliber handgun he used in the Feb. 15 shooting at Henry Pratt Co. in Aurora.

The Mississippi conviction was only discovered when Martin was fingerprinted to expedite his concealed carry license in March 2014. His owner's permit was rescinded, and state police say they notified him in April 2014 that he wasn't supposed to possess a gun anymore.

State police said an "exhaustive search" didn't find Martin's returned owner's permit or the record detailing how he relinquished his handgun.