President Barack Obama jumpstarted the holiday season, lighting the National Christmas Tree but also appealing to Americans to "come together as brothers and sisters" a day after 14 people were shot to death in California.
"This is of course the most wonderful time of the year, but we would be remiss not to take a moment to remember our fellow Americans whose hearts are heavy tonight, who grieve for loved ones, especially in San Bernardino, California," Obama said.
"Their loss is our loss, too. We're all one American family," he added.
Moments earlier, the president, his wife, Michelle, daughters Malia and Sasha, and his mother-in-law, Marian Robinson, together flipped a switch and illuminated the Christmas tree near the White House.
As a backdrop to the ceremony, the US flag flew at half-staff atop the White House, on Obama's orders, in remembrance of the California victims.
Obama closed the ceremony by taking over the microphone to help Santa Claus belt out "Jingle Bells."
Actress Reese Witherspoon served as host. Musicians Crosby, Stills and Nash, Kelsea Ballerini and Fall Out Boy also performed.
