SAN FRANCISCO (CN) - Inspired by more than 150 school shootings since 2012, California Lt. Gov. Gavin Newsom announced a sweeping gun-control ballot measure Thursday that would require background checks for ammunition purchases and strengthen the state's assault weapons ban.
The Democratic candidate for governor in 2018 introduced the initiative in downtown San Francisco Thursday, at the site of a mass shooting in 1993 that killed nine people. Newsom's initiative, the Safety for All Campaign, has 90 days to collect 365,880 signatures to place it on the November 2016 ballot.
"I just don't get why people need 11-plus rounds of ammunition in a military-style assault weapon magazine," Newsom told reporters. "You can't sell or manufacture those magazines in California, but for some reason we've allowed people to possess them."
While California expanded its assault weapons ban in 1999 and prohibited extended magazines, owners were allowed to register and keep the weapons. Newsom's plan would force owners to turn in the prohibited magazines to law enforcement agencies or sell them to a firearms dealer - similar to current laws in New York, New Jersey and the District of Columbia.
The proposal also calls for background checks for ammunition purchases and licensing for ammunition retailers. If the measure succeeds, California would become the first state to require background checks on ammunition purchases.
"We want to create some common-sense reforms that would protect the public," Newsom said.
Newsom, who has previously tackled other contentious issues such as the legalization of marijuana and marriage licenses to same-sex couples, worked with the Law Center to Prevent Gun Violence in San Francisco to create the gun-control proposal.
Shortly after Newsom's press conference, an officer-involved shooting occurred blocks away and forced the closure of Market Street in San Francisco. Medical examiners and homicide detectives were dispatched although the San Francisco Police Department did not immediately announce details on the shooting.
A National Rifle Association spokeswoman told Courthouse News Newsom's plan "illustrates the true gun control agenda, which is the ultimate confiscation and banning of firearms."
"If Gavin Newsom gets his way, the state will be the next Australia. His ballot initiative proposal does nothing but prohibit access to the most effective methods for self-defense, with no measurable positive effect on stopping crime or improving public safety. They can't repeal the Second Amendment, so they're trying to chip away our rights until there is nothing left," she said.
A recent poll by the Public Policy Institute of California found 65 percent adults feel California's gun control laws should be stricter and 57 percent responded that regulating gun ownership is more important than protecting the right of Americans to own guns.
Read the Top 8
Sign up for the Top 8, a roundup of the day's top stories delivered directly to your inbox Monday through Friday.