Below is a sampling of the early reactions the candidates offered on Twitter. We'll update our rundown as we get more comments.
Later in the afternoon, at an event in South Carolina, Ben Carson described the San Bernardino shooting as "another hate crime."
"At least 14 people killed," he added. "Less than a week ago we had the shooting in Colorado. Look at the things that are going on around the world… Just hatred and evil. We need to be able to combat these things because otherwise we will melt into despair and that’s not who we are."
Asked later why he had classified Wednesday's shooting as a hate crime, Carson elaborated: “It’s hard to imagine that you would shoot a bunch of people if you didn’t hate them," he said. "You don’t do that to people you love.”
As law enforcement confronted shooting suspects, Trump tweeted again, saying later he would pay tribute to the victims at his campaign rally in Virginia Wednesday evening:
Jose DelReal in Spartanburg, S.C. contributed to this report.