While the suspect had encounters with local law enforcement officers that led to the temporary confiscation of knives, he wasn’t charged with or convicted of a crime, meaning he most likely would have passed an FBI background check, two congressional aides said.

But experts say a key provision in the law for gun buyers under 21 requires a threefold check, including contacting local law enforcement agencies in the city where the person resides (and checking for any disqualifying juvenile criminal or mental health records). That would have been enough to tip off police in Illinois that the suspect was trying to buy a gun so they could use the state’s “red flag” law to keep firearms out of his hands.

“It’s not clear whether it would have prohibited the purchase,” said Nick Suplina, the senior vice president of law and policy for Everytown for Gun Safety. “But it may have led to other action from law enforcement — at least a flag that, hey, this young man that threatened to kill his family and himself is purchasing a gun.”

The suspect was known to Highland Park police; officers twice visited his family’s home in 2019.

The first visit came in April of that year, when law enforcement officers followed up on a report that he had attempted suicide, authorities said. The incident was handled by a mental health professional.

In September 2019, police visited the home again after a family member reported that the suspect had threatened to kill his relatives. Sixteen knives, a sword and a dagger were confiscated, authorities said, but the suspect wasn’t arrested because family members declined to sign any complaints.

He successfully applied for a gun license in December of that year, when he was 19, Illinois State Police said; his father sponsored his application. After that, the suspect passed background checks and was able to purchase five firearms in 2020 and 2021, including the AR-15-style rifle that police say was used to gun down dozens of paradegoers and spectators celebrating Independence Day.

“Under the new law, because he was under 21, local law enforcement would have been contacted as part of the enhanced background checks. That is relevant because he was known by local law enforcement, because on two separate occasions law enforcement came to his home. One was for an attempted suicide,” said Brian Lemek, the former executive director of Brady PAC.

“Those visits may have been enough to trigger” an extreme risk protection order or a red flag law order allowing authorities to confiscate his guns.

Other provisions of the federal gun law also could have affected the sequence of events, albeit indirectly. The main one is the funding grants that can be used to enforce red flag laws, which the chief Democratic author said must be better implemented to work.

Illinois adopted a red flag law in 2019 that allows family members or law enforcement officials to petition courts to issue “firearm restraining orders,” which prevent people from buying or possessing firearms if they pose a danger to themselves or others. But an order was never sought in the suspect’s case, even though he had threatened to harm himself and others.

“Illinois has on the books a red flag law, but it’s a law that is not utilized very often,” Sen. Chris Murphy, D-Conn., an author of the gun law, said Tuesday evening on CNN. “It’s an ineffective program. The bill we just passed through Congress a week and a half ago appropriates almost $1 billion to help states like Illinois teach law enforcement and first responders to use a red flag law well.

“If everybody knew how to use Illinois’ red flag law, would they have used it in this case? Because it certainly does appear there was enough information about this young man to cause a court, to cause law enforcement, to go in and take his guns away,” Murphy said. “A well-run red flag law might have done the trick here.”

Robin Lloyd, the managing director of the gun safety group Giffords, agreed that hundreds of millions of dollars in federal grants will help states strengthen and grow awareness about new and existing red flag laws.

“A law like that law in Illinois is only as good as it’s implemented,” Lloyd said in an interview. “If law enforcement, family members and other stakeholders don’t know about that law, then it’s not going to be utilized,” and “it’s limited in its effectiveness.”

According to Illinois State Police data circulated by Gov. J.B. Pritzker’s office, the suspect’s only criminal offense was a violation for tobacco possession in January 2016, and police had received no mental health reports involving him.

The governor’s office added that the September 2019 “clear and present danger report” came in response to threats he made but that he told police that he didn’t feel like harming himself or others. And they returned the knives to his father after he claimed they were his.

"Unfortunately, every time a mass shooting occurs it serves as a stark reminder that our gun laws often fall short of the rigorous standards that feel like common sense to most Americans,” Pritzker said in a statement.

“I call on all Illinoisans to learn about and use the Illinois Firearm Restraining Order Act already in law to alert authorities to dangerous individuals with guns. My administration will work with the General Assembly to ensure we take on the gun lobby and do everything we can to further strengthen our gun control and red flag laws.”

Pritzker further called on Congress to regulate “weapons of war and high capacity magazines that are used only for mass murder,” saying that Illinois may have strict gun laws but that it is “only as safe as the state with the weakest laws — many of which border Illinois.”

Igor Volsky, the executive director of the anti-gun-violence advocacy group Guns Down America, said it was “absolutely scandalous” that gun buyers can still purchase weapons like the one used to carry out the Highland Park attack. But he acknowledged that the new federal law didn’t set out to ban such guns.

“We knew from the very beginning that we were talking about a fairly narrow set of reforms to garner bipartisan support,” Volsky said of the law, which passed the Senate with all 50 Democratic-voting senators and 15 Republicans.

“Obviously, we know there are lifesaving provisions in that law that will prevent others from causing harm, so that’s not to take away from it,” he said. “But I think we as a country have a lot further to go in terms of strengthening our gun laws.”