Obama to perform sad duty -- again

Once again, President Obama on Sunday performs the saddest of White House duties -- comforting the survivors of senseless shootings.

The president travels to Newtown, Conn., to speak at an interfaith vigil for the victims of Friday's mass killing at Sandy Hook Elementary School.

The service is scheduled for 7 p.m. ET.

Obama will also meet privately with relatives of the 26 people killed, including 20 children.

It's the fourth such tragic journey for the president.

Obama spoke following the 2009 serial shooting at Fort Hood, Texas, which killed 13 servicemembers; the 2010 shooting in Tucson that killed six people and wounded Rep. Gabrielle Giffords, D-Ariz., and the July shooting at a movie theater in Aurora, Colo., that left 12 people dead.

In Aurora, Obama visited survivors in the hospital and later told reporters: "Even in the darkest of days, life continues and people are strong."

In his radio address Saturday on the Connecticut killings, Obama said: "As a nation, we have endured far too many of these tragedies in the last few years."