As many as three gunmen wearing vests and masks opened fire late Wednesday morning inside the Inland Regional Center, a state-run social services facility in San Bernardino, California. Local law enforcement has said that 14 victims are dead and another 17 have been wounded.

San Bernardino Police Chief Jarrod Burguan said the shooters targeted a group of county employees who were renting out a conference center in the facility. He added that the attackers “came prepared to do what they did as if they were on a mission.”

In the latest development, law enforcement teams in armored vehicles have cornered a black SUV believed to hold three suspects. Unconfirmed reports say that one of the gunmen is dead and another is in custody, with the status of a third unknown.

Here’s the livestream from Fox 11. More context after the feed.

There are reports of three heavily armed shooters

Officials said the attackers used long guns, and are on the run.

The involvement of more than one shooter would mark this event as an anomaly

In the vast majority of cases, mass shooters act on their own.

An FBI study of active shooter incidents from 2000 to 2013 found that in 160 shootings, only two involved more than one gunman. The most infamous incident to involve multiple shooters was the Columbine High School shooting in Colorado, in 1999.

False reports of multiple shooters often emerge in the immediate aftermath of high-profile massacres. This happened following the Sandy Hook shooting and the Washington, D.C., Navy Yard shooting, both of which were carried out by a lone gunman.

Another unusual aspect of this mass shooting is that the perpetrators fled the scene: The FBI study found that in only 25 out of 160 active shootings did the perpetrator manage to leave the area before police arrived.

“They came prepared to do what they did as if they were on a mission.”

Jarrod Burguan, San Bernardino Police Chief

Today’s massacre is already the fifth deadliest mass shooting in U.S. history

Local police said in a press conference this afternoon that they have confirmed at least 14 victims died in today’s mass shooting. That makes it the fifth deadliest shooting in U.S. history. The 2007 Virginia Tech shooting resulted in the most deaths, with 32 dead. That massacre is followed by the 2012 Sandy Hook shooting, where 27 died; the Killeen, TX shooting in 1991, where 22 died; and the 1984 San Ysidro, CA shooting, where 21 died. A 1986 shooting in Edmond, OK also resulted in 14 deaths.

It’s also the 355th mass shooting so far this year and the fifth in the last week, according to the Mass Shooting Tracker, a crowdsourced database of incidents in which four or more people are shot.

San Bernardino has struggled with gun violence for years

Today’s mass shooting in San Bernadino is the most high-profile incident of gun violence in a city that has struggled with the issue for years. Local residents lamented this August that city officials have done little to stem the problem.

Lieutenant Rich Lawhead of the San Bernardino Police Department believes that a confluence of factors is driving the city’s gun violence. “This is kind of a perfect storm right now,” he told the San Bernardino Sun in July 2014.

As part of a plan to reduce California’s prison population, the city has seen an influx of felons who were recently released from jail. And as Los Angeles cracks down on its gang problem, many of those trying to flee law enforcement have relocated their drug operations to desert cities like San Bernardino. At the same time, San Bernardino’s police force has been slashed because of budget problems, leaving just more than 300 officers to patrol a city of 200,000 people. The combination of a growing criminal population, illegal gang activity, and dwindling law enforcement ranks has led to an uptick in gun violence, according to Lawhead.

The city had 46 homicides in 2013, and 30 homicides in 2014. Most of the victims were connected with gangs or illegal drug activity. The Gun Violence Archive has recorded 37 instances of gun violence in San Bernadino this year alone, with 13 fatalities and 24 injuries. From 2006 to 2010, the city’s gun homicide rate was twice as high as San Diego’s.

Californians may soon vote on a set of ballot initiatives that would impose tough new gun restrictions

This shooting comes as California’s Lieutenant Governor, Gavin Newsom, is gathering signatures for a ballot initiative that would seek to reduce gun violence with a range of policies. The initiative would ban not only the sale and transfer but also the possession of magazines that hold more than 10 rounds of ammunition. Newsome is also calling for retailers of ammunition to acquire federal licenses like gun dealers, mandatory reporting of lost or stolen firearms, and a better system to recover guns from those prohibited from possessing firearms because of certain criminal records.

The presidential candidates are weighing in

See the statements of other candidates at The New York Times.

President Barack Obama made his 17th set of remarks following a mass shooting

In an interview with CBS from the climate conference in Paris, President Obama delivered his 17th set of remarks following a mass shooting in the U.S.:

The one thing we do know is that we have a pattern now of mass shootings in this country that has no parallel anywhere else in the world. And there’s some steps we can take not to eliminate every one of these mass shootings but to improve the odds that they don’t happen as frequently. Common sense gun safety laws, stronger background checks — and for those who are concerned about terrorism, some may be aware of the fact that we have a no-fly list where people can’t get on planes, but those same people who we don’t allow to fly could go into a store right now in the United States and buy a firearm, and there’s nothing that we can do to stop him. That’s a law that needs to be changed.

House Speaker Paul Ryan also addressed the shooting as he spoke at the Capitol during a Christmas Tree lighting ceremony. After noting that the warm November weather in DC compared to a “nice night in July” in Alaska, where the tree was harvested, Ryan asked for a moment of silence in honor of the shooting’s victims. Then he discussed the tree.

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[Photo: Gina Ferazzi / Los Angeles Times via Getty Images]