The perpetrators, Syed Rizwan Farook and Tashfeen Malik, a married couple living in the city of Redlands, targeted a San Bernardino County Department of Public Health training event and Christmas party of about 80 employees in a rented banquet room.

[17] Sources reported that Malik pledged bay'ah (allegiance) to Abu Bakr al-Baghdadi, the leader of Islamic State of Iraq and the Levant (ISIL), on a Facebook account associated with her as the attack was underway.

A witness gave Farook's name to police, who quickly learned that he had rented a black Ford Expedition EL SUV with Utah license plates four days before the attack.

[1][50] The SUV exited the freeway onto North Tippecanoe Avenue and briefly stopped at a stoplight, where a pursuing officer observed the perpetrators putting on tactical vests and equipping themselves with rifles.

San Bernardino Police Chief Jarrod Burguan said in an interview with ABC News that Malik stated that "she didn't think that a Muslim should have to participate in a non-Muslim holiday or event" in an online account.

[109] On December 10, 2015, federal authorities began searching Seccombe Lake park in downtown San Bernardino after receiving a tip that the shooters visited the area on the day of the attack.

The FBI responded by successfully applying to a United States magistrate judge, Sherri Pym, to issue a court order, mandating Apple to create and provide the requested software.

[141][142] However, The Washington Post, citing anonymous sources, reported that the FBI instead paid "professional hackers" who used a zero-day vulnerability in the iPhone's software to bypass its ten-try limitation, and did not need Cellebrite's assistance.

[144] In September 2016, the Associated Press, Vice Media, and Gannett (the owner of USA Today) filed a Freedom of Information Act (FOIA) lawsuit against the FBI, seeking to compel the agency to reveal who it hired to unlock Farook's iPhone, and how much was paid.

[156] Enrique Marquez Jr.,[157] a next-door neighbor of Farook's until May 2015,[158] and who is related to him by an immigration fraud sham marriage,[159] was investigated in connection with his purchase of the two rifles used in the attack,[160][161][162][163] a charge to which he agreed to plead guilty.

[158][167] Federal prosecutors allege that in 2011, Farook and Marquez conspired to carry out shooting and bombing attacks at the library or cafeteria at Riverside Community College, where both were students, and on rush-hour traffic on California State Route 91 in Corona.

[173][174] By 2011, Marquez spent most of his time in Farook's home, listening to, watching, and reading radical Islamist propaganda, including Inspire magazine, the official publication of Al-Qaeda in the Arabian Peninsula (AQAP), and videos produced by Al-Shabaab as well as the sermons of Anwar al-Awlaki.

[159] In February 2017, as part of a plea agreement with federal prosecutors, Marquez pleaded guilty to conspiracy to provide material support to terrorists and to making false statements in connection with the purchase of a firearm.

[198] In January 2017, Raheel Farook pleaded guilty to one felony count of conspiracy to commit immigration fraud, arising from his making of a false statement in support of Chernykh's application for permanent residency.

The FBI recovered what prosecutors called the "attack plan" from a shredder in Raheel Farook's home in Corona and reconstructed it using a computer and scanner, according to Assistant U.S. Attorney Christopher Grigg.

It also listed action items such as practicing at a shooting range, destroying electronics that authorities could use for tracking, purchasing parts to construct IEDs, and transferring funds to Shareef's bank account.

"[204] On March 18, 2016, California State Assemblyman Freddie Rodriguez of the Joint Legislative Committee on Emergency Management conducted a hearing in which first responders were to share details of the response to the attack and possible aspects that could be improved on.

[206][207] President Barack Obama called for "common sense" gun safety laws and stronger background checks as part of a bipartisan effort to reduce the frequency of such shootings.

[219] The Times editorial board wrote: "It is a moral outrage and a national disgrace that civilians can legally purchase weapons designed specifically to kill people with brutal speed and efficiency.

"[220] Arthur O. Sulzberger, Jr., publisher of the Times, said the placement of the editorial on the front page was "to deliver a strong and visible statement of frustration and anguish about our country's inability to come to terms with the scourge of guns.

[252] The City of San Bernardino incurred up to US$1 million in unforeseen expenses (such as the deployment of more police officers on extended shifts) as a result of the attack, and planned to seek state and federal emergency funds to help cover the costs.

[258][259] On January 4, 2016, a memorial for the slain victims was held at the Citizens Business Bank Arena in nearby Ontario, with thousands in attendance, including Governor Brown, California Attorney General Kamala Harris, former New York City mayor Rudy Giuliani, and Christian pastor Rick Warren.

[263] President Barack Obama ordered U.S. flags to be flown at half-staff at the White House, public buildings, military installations, Navy ships, embassies, and diplomatic missions.

[273][274][275] In the aftermath of the shooting, CAIR reported an escalation in anti-Muslim hate crimes in the U.S., including the throwing of a pig's head at a mosque in Philadelphia, the beating of a Queens shop owner, and incidents of death threats and vandalism.

"[238] On September 12, 2016, Brown and California Attorney General Kamala Harris awarded eight police officers the Medal of Valor for their roles in emergency response during the attack and the subsequent shootout with the perpetrators.

[284]In an address to the nation delivered from the Oval Office on December 6, 2015, President Obama declared the shooting an act of terrorism, referring to the shooters as having "gone down the dark path of radicalization" and embracing a "perverted version of Islam".

"[289] In the New York Review of Books, Wyatt Mason observed that a mass shooting at a Colorado Springs Planned Parenthood clinic, committed by a devout Christian a week earlier, did not lead to the kind of rhetorical outpouring produced by the San Bernardino attack, and argued that the difference in response suggested racism was at work.

That's something I'll continue to talk about in the weeks ahead.In response to the shooting, then-candidate Donald Trump called for a "total and complete" ban on Muslims entering the United States "until our country's representatives can figure out what is going on.

[304] The attack reignited the debate over whether U.S. government should expand electronic surveillance of Americans, and specifically whether Congress should adopt legislation mandating that technology companies provide a backdoor so that law enforcement has access to encrypted communication.

[305] At a December 9, 2015, hearing before the Senate Judiciary Committee, FBI Director Comey called upon tech companies offering end-to-end encryption (such as Apple) to revise their "business model".