Australia had a big shooting so they put laws to restrict guns. It was super effective. California is another example.
https://cdn.americanprogress.org/content/uploads/2019/11/18061930/CaliforniaGunViolence-Factsheet.pdf
Center for American Progress |California Gun ViolenceCalifornia Gun Violence November 2019 Gun violence takes a devastating toll on California
From 2008 through 2017, 30,703 people were killed with guns in California.
From 2014 through 2018, there were 186 mass shootings in California. A total of 198 people were killed and 757 were injured.
California has some of the highest levels of gun-related crime in the country From 2008 through 2017, a gun homicide occurred every six hours.
Law enforcement officers in California face an enormous risk of gun violence. From 2008 through 2017, 37 police officers were feloniously killed with a firearm in California.
The burden of gun violence in California falls disproportionately on communities of color:
Approximately 32 percent of the state’s gun homicide victims are Black; however, only 6 percent of the state’s population is Black.
While Hispanics make up close to 38 percent of the state’s population, they account for approximately 47 percent of gun homicide victims in the state.
In 2017, handguns were involved in the majority (64%) of the 10,982 U.S. gun murders and non-negligent manslaughters for which data is available, according to the FBI. Rifles – the category that includes many guns that are sometimes referred to as “assault weapons”– were involved in 4%. Shotguns were involved in 2%.
From Pew
In other words California gun laws don't matter to people that break laws and creating new laws does nothing to deter the violence it only penalizes those operating under said laws.