CNN — The deadly mass shooting that unfolded Wednesday following a Super Bowl celebration rally in Kansas City – a city that recorded its deadliest-ever year in 2023 – occurred in a state known to have some of the weakest gun laws in the country.

The gunfire killed a 43-year-old woman and injured at least 23 others during a Kansas City Chiefs parade where around 1 million people gathered to celebrate, and prompted calls from the Biden administration for Congress to pass “reasonable gun safety laws.”

“What are we waiting for? What else do we need to see? How many more families need to be torn apart?” President Joe Biden said in a statement Wednesday.

The lax gun laws in Missouri, where at least 155 mass shootings have happened since 2013, have created challenges for law enforcement and officials in preventing and investigating gun violence in the state. Here’s why.

Missouri’s weak laws have led to gun deaths spike

While Missouri does have partial open carry regulations and certain child access prevention laws in place, the Giffords Law Center to Prevent Gun Violence has said the state’s gun laws are “appallingly weak.”

Missouri ranks 38th among the 50 states when it comes to gun law strength; California leads the country with the toughest enacted gun laws and Arkansas ranks at 50 for the weakest, according to Everytown for Gun Safety.

The gun control advocacy and gun violence prevention-focused nonprofit says Missouri, which is among the top 10 states with the most firearm-related deaths, lacks any “of the foundational gun violence prevention laws” – including passing background checks and/or purchase permitting, secure gun storage requirements, requiring a concealed carry permit, Extreme Risk laws and rejecting Shoot First laws.

Extreme Risk laws, also called Red Flag laws, temporarily prevent a person in crisis from accessing guns by letting police or loved ones intervene through petitioning a court order.

Shoot First laws, or Stand Your Ground laws, “allow people to shoot and kill in public even if they can safely walk away from the situation,” according to Everytown.

The state’s 2007 repeal of an 80-year-old permit-to-purchase law led to around a 27% rise in the state’s gun homicide rate, according to Everytown.

“Missouri is a gun rights paradise, but this clearly has public safety implications,” said Jennifer Mascia, a CNN contributor and senior news writer at The Trace, a nonprofit journalism outlet focusing on gun-related news.

The state’s gun laws were rolled back specifically to prevent incidents like Wednesday’s shooting – “to allow ‘good guys with guns’ to easily access weapons and defend themselves and their communities,” Mascia said.

But today, Mascia noted, Missouri has one of the highest gun-death rates in the United States.

The state’s lax gun laws have allowed for firearms to reach criminal hands through legal gun owners by way of theft, private sales and straw buyers, Mascia explained.

“There’s no mechanism in our laws to periodically check in with gun owners and make sure they’re properly handling their guns, and locking them up and reporting thefts,” she said. “That’s especially true in Missouri, where you can buy a gun in a private sale and carry it in public with no background check and no authorities ever being notified.”

How Missouri’s gun laws make crime investigation difficult

While some leaders, including Kansas City Mayor Quinton Lucas and St. Louis Mayor Tishaura Jones, have pushed back against Missouri’s restrictions on its cities’ ability to fight gun violence, the state – which controls law enforcement in Kansas City – has made it “nearly impossible” for cities to do so, according to Everytown.

The state enacted the Second Amendment Preservation Act in 2021, which would subject local and state law enforcement officers to $50,000 fines for helping to enforce a federal gun law, according to the Giffords Law Center.

However, in a 24-page decision last March, US District Judge Brian Wimes ruled the law is “invalidated as unconstitutional in its entirety,” CNN previously reported.

The US Supreme Court rejected an emergency petition by the State of Missouri to block Wimes’ decision.

Missouri cities, including Kansas City, can’t pass their own gun laws; only the state legislature can, according to Mascia.

“But cities have been trying: Several initiatives vying for the Missouri ballot in November would reinstate the ability of cities to make their own gun laws — specifically Kansas City and St. Louis,” she said.

Missouri lawmakers have also introduced several gun-related bills during the 2024 state legislative session, including legislation to lower the age requirement for carrying a concealed firearm from 19 to 18 and legislation to allow the state to take control of municipal law enforcement agencies from city government – a measure that “would frustrate the ability of Missouri cities to combat gun violence,” according to Everytown.

Following Wednesday’s deadly shooting in Kansas City, police face the critical challenge of not only determining whether firearms recovered at the scene were fired during the mass shooting, but also linking each weapon to a specific shooter.

Permissive gun laws make this even more challenging because weapons can easily change hands without registration requirements that would allow police to quickly trace the owner of a firearm.

Bullets, shell casings are major focus of investigation

Specialists from the Bureau of Alcohol, Tobacco, Firearms, and Explosives are also analyzing bullets recovered at the scene and from victims to determine which gun was responsible for killing or injuring specific people, a law enforcement source told CNN.

Ejected casings are additionally being studied to identify whether unique markings left behind on a shell casing by a gun during firing – similar to a fingerprint – match other shootings in law enforcement databases, the source said.

In addition to helping tie those guns to rounds fired at the scene, the source said ATF investigators are working to determine whether any bullets and shell casings recovered fail to fit the unique profile of those recovered weapons, which could indicate additional suspects are at large.

But even if a firearm associated with Wednesday’s mass shooting does match with a weapon in the ATF’s database of previous shootings, the absence of any laws in Missouri requiring registration, coupled with the ability of gun owners to anonymously transfer weapons through private sales, does not guarantee police will be any closer to identifying the person who pulled the trigger.

CNN’s Ariane de Vogue and Devan Cole contributed to this report.