Assault rifles, or AR-15’s, have been used to carry out some of the deadliest mass shootings in America, so when San Bruno police department got word of shots fired at a YouTube campus Tuesday, they feared the worst.

“We may have thought that we were going to encounter someone with maybe a rifle or something like that,” said San Bruno Police Chief Ed Barberini.

But in this instance there was no assault rifle. Instead, Nasim Aghdam, a 39-year-old vegan activist, after practicing at a shooting range, drove to YouTube armed with a Smith & Wesson 9 millimeter semiautomatic handgun that she had purchased legally and licensed in her name. After opening fire and wounding three people, none fatally, she turned the gun on herself.

California is known for having the most stringent gun laws in the United States, which includes a ban on assault rifles such as the AR-15 instituted in 1989. That means that while it’s not impossible to possess an illegal assault rifle in California, as the mass shooters in San Berdardino in 2015 did, you cannot own one legally.

The state also bans the sale or manufacture of ammunition magazines that can hold more than ten cartridges or rounds, which gun owners sometimes use to accessorize their assault weapons and unleash bullets in quick succession.

“Certainly we were better off that she had a 9 millimeter handgun instead of an AR-15”

“Certainly we were better off that she had a 9 millimeter handgun instead of an AR-15,” said Stanford University law professor John Donahue. “We are always better off in these mass shooting incidents if the person doesn’t have a high capacity magazine.”

Weapon of war

The deadliest mass shootings in recent years, from Sandy Hook in 2013, to Las Vegas last October, to Parkland, Florida in February, have been carried out with AR-style rifles. “They [AR-15s] are the Formula One cars of guns, designed to kill as many people as quickly and efficiently as possible,” 20-year combat veteran Joe Penzler recently told the New York Times. “We are seeing battlefield-level casualties because we are allowing those weapons on our street.”

The research shows that assault rifle bans don’t decrease the number of gun homocides, they do make mass shootings with four or more casualties less likely.

“The ban on assault weapons hasn’t been associated with reductions in homicides in research,” said April Zeoli, an associate professor at Michigan State University’s School of Criminal Justice. “But researchers do have reason to believe that reducing availability in assault weapons will reduce the number of people killed in a mass shooting situation.”

Acquiring any kind of firearm in California is also much more difficult than it is in other states. For example, if you want to buy a gun, you have to take and pass a written safety test that costs $25. Regardless of your place of purchase, your application to purchase a firearm will be sent to the state’s Department of Justice for a background check. If you’re cleared, after ten days, you need to get your gun microstamped, which means the firearms serial number will be imprinted on every bullet casing it fires. Only then will you be able to take it home.

Zeoli was not particularly surprised that Aghdam was a licensed gun owner. “One of the things we know about people who commit shootings in general is that, in many cases, that shooting is committed with a firearm that they legally own,” said Zeoli.

Red flag

California was also one of the first five states to adopt a “red flag law” which seeks to keep guns out of the hands of those who have a history of violence, domestic abuse, violent ideation or mental illness which leads relatives or law enforcement to believe they may inflict harm upon themselves or someone else. In this instance, police said that they had no indication or suspicion that Aghdam planned to do something violent, and therefore there was nothing that would have triggered the process by which a court can confiscate someone’s guns.

“[The law] does require some action on the part of the police and the parents to highlight the nature of the threat,” said Donahue. “Once a family member tells the police, they can move in and take the gun away.”

On Tuesday, talking heads on NRA-TV pored over the scant information publicly available about the YouTube shooting and gunwoman. NRA correspondent Chuck Holton argued that California’s strict gun laws didn’t make a difference in the YouTube shooting. “Liberals are always trying to fight the last battle and not the next one,” said Holton. “In this case, age restrictions wouldn’t have done anything. California has a ban on assault rifles. They have a ban on high-capacity magazines. There’s a 10-day waiting period for any firearm purchase.”

Zeoli doesn’t buy that logic. “The argument that if one shooting cannot be stopped by firearm restrictions, then the law is worthless is not a sound argument,” he said. “Research has shown that many of the laws that California has are associated with reductions in homicides." The Gifford’s Law Center, an organization that advocates for gun control, also links California's gun laws with its lowered gun death rate.

“The fact that this one got through. It’s unfortunate,” said Zeoli. “But it doesn’t mean that the laws are bad or not working.”