Photo: Cem Ozdel/Anadolu Agency/Getty Images
The perpetrators, identified as Syed Rizwan Farook and his wife Tashfeen Malik, were eventually killed in a gun battle with the police.
Farook worked at the Inland Regional Centre, and most of the victims were his coworkers and county employees, who were attending a holiday party.
Though no clear motive has been established yet, authorities hint that this was a case of religious extremism.
But whatever be the motive in this particular case, one cannot deny that gun violence is a common occurrence in the US these days, and has killed more people in the country than terror attacks in the last decade.
This was the 355th incident of mass shooting in the US in this calendar year, and the deadliest such incident since the Newtown school shootings in Connecticut in 2012.
Here are a few more statistics that highlight the growing menace of gun violence in the US.
In 2014, 336 shootings took place. The year before that, the number was 363.
The number of people killed in mass shootings in 2014 was 462, and the number of injured persons was 1,312.
Disturbingly, gun killing rates for a few US cities is higher than those of many nations which are considered 'dangerous'.
Additionally, each year about 4.5 million guns are sold in the US. This excludes two million second-hand guns.
Though the US accounts for 5% of the world's population, it hosts 35-50% of the world's civilian guns.
Gun homicides in the US are the second leading cause of death among the 15-24 age group. They are also the main cause of death among black Americans.
Taxpayers bear almost half ($ 1.1 billion) the medical costs for gunshot injuries.
Gun violence has many sociological impacts. Apart from medical costs, the costs of the criminal justice system, money spent on security precautions like metal detectors, it also affects the quality of life due fear psychosis, according to Heeding God's Call, an organisation fighting to end gun violence.
Substance abuse, child abuse and alcoholism increase the risk of violent crime.
A 2011 research by US economist Richard Florida found that states which had tighter gun laws had lesser gun deaths. However, the disclaimer is that correlation does not necessarily mean causation.
"In 2014, less than half of Americans, 47%, said they favour stricter laws covering the sale of firearms, similar to views found last year. But this percentage is significantly below the 58% recorded in 2012, after the school shooting in Newtown, Connecticut," said a Gallup survey.
87 people have been killed in these 248 shootings.