A Colorado congressman wants to close the loophole in the federal gun background check system that allowed 18-year-old Sol Pais in 2019 to purchase a shotgun in Littleton, prompting panic and school closures because authorities feared her obsession with the 1999 Columbine shooting would prompt her to commit similar violence.

The bill introduced Wednesday by Rep. Joe Neguse, a Lafayette Democrat, would update the National Instant Criminal Background Check System so that it checks potential gun buyers’ eligibility in their home states as well as their eligibility in the state where they are purchasing the gun. Pais was eligible to purchase the shotgun in Colorado but would not be eligible for the same purchase in her home state of Florida, which bans gun sales to anyone under age 21.

The Secure Background Checks Act would add state-level age requirements to the federal background check so that underage would-be gun buyers can’t simply travel to another state to buy a gun they are prohibited from buying in their home state.

“We have a gun violence epidemic in our country today, and taking steps to prevent it is absolutely essential,” Neguse said in a news release. “By making this simple fix, we hope to improve the federal background check system and keep firearms out of the hands of folks who the law says shouldn’t have them.”

Neguse’s bill is the legislative response to problems identified in a U.S. Department of Justice report on the Sol Pais incident released last month. The investigation found that the shop that sold Pais her gun did not double-check laws in Pais’s home state and that there is no failsafe when a gun seller makes such an error.

Neguse and five other Colorado congressmen requested the investigation after the Pais incident in April 2019.

Pais traveled to Colorado on April 15, 2019 — five days before the 20th anniversary of the Columbine High School shooting — on a one-way plane ticket and purchased the shotgun at Colorado Gun Broker. After an extensive search for the girl, law enforcement found her body two days after her arrival near a trail on Mount Evans. Authorities believe she died by suicide on the day she arrived in Colorado.

Neguse’s bill is co-sponsored by Rep. Ed Perlmutter, an Arvada Democrat, as well as three other Democratic lawmakers. The bill has the support of more than a dozen gun violence prevention organizations, according to Neguse’s office.

“This common-sense bill closes a simple one: if you’re too young to purchase a gun in your home state, a federal background check should catch that and help enforce those laws,” Shannon Watts, founder of Moms Demand Action, said in a news release.