JUDY WOODRUFF: A student walked into a high school in suburban Denver today armed with a shotgun and shot two other students before apparently killing himself.

Authorities in Arapahoe County have not identified the gunman yet, but did say he was looking for a specific teacher. Students were seen walking away from the school with their hands in the air as the building was evacuated. Arapahoe County Sheriff Grayson Robinson explained the procedure.

GRAYSON ROBINSON, Arapahoe County, Colo., Sheriff: Think were they were safer inside their locked schoolroom classes then they would have been had we allowed them to exit. And that was part of our strategyand part of our protocol. We are now slowly, but methodically allowing students to leave the school in groups.

JUDY WOODRUFF: Today's incident falls just one day before the one-year anniversary of the Newtown, Connecticut, elementary school shooting. And it happened just eight miles from Columbine High School, where twoteenagers killed 12 classmates in 1999.

Federal authorities arrested a man in Kansas today on suspicion he was plotting a suicide attack on an airport in Wichita on behalf of al-Qaida. Officials charged Terry Loewen, a 58-year old aviation technician, with attempting to use a weapon of mass destruction and providing support to a foreign terrorist organization.

U.S. attorney Barry Grissom outlined some of what Loewen allegedly planned to do.

BARRY GRISSOM, U.S. Attorney: He researched flight schedules to determine when there would be a maximum number of individuals at the airport. He -- he assisted in acquiring components which he believed were part of the building of the bomb. He talked about his commitment to this crime and his commitment to martyrhimself as part of this horrific event.

JUDY WOODRUFF: Officials said they were continuing their investigation, but no further arrests were expected.

The family of a missing American man with secret ties to the CIA urged the U.S. government to take care ofits own today. Robert Levinson vanished in Iran nearly seven years ago. An investigation by the AssociatedPress found that he was working for the CIA on an unapproved intelligence-gathering mission.

For years, the U.S. has publicly described him as a private citizen on private business. We will dig deeper into the AP's findings with the editor of the story after the news summary.

In Syria today, soldiers surrounded an industrial area near Damascus to fend off attacks from an al-Qaida-linked rebel group. The action took place in Adra, northeast of the capital. Rebels reportedly killed workers and their families who live there and largely support President Assad.

Ukraine's embattled president held talks today with opposition leaders in an effort to resolve a three-week-long political crisis. It stemmed from Viktor Yanukovych's decision to scrap a trade deal with the European Union. During today's meeting, Yanukovych said he will sign it, and he also offered amnesty to protesters facing criminal charges. But the opposition said those promises still fall short.

French troops battled rebel fighters in the Central African Republic's capital today. Some 1,600 French peacekeepers are working to disarm the rebels and restore calm to Bangui. Violence between Christians and Muslims has left more than 500 people dead just in the past week. About 160,000 others were forced to leave their homes.

RACHEL DIMAGUE, police officer (through interpreter): There's a lot of shooting here. We don't knowhow tolive anymore. The children have left to take refuge. We are a country at war.

JUDY WOODRUFF: U.N. Secretary-General Ban Ki-Moon pleaded for an end to the bloodshed during a radio message to the country. He warned, the world was watching and would hold them accountable.

Today was the third and final day for mourners to pay respects to Nelson Mandela as he lay in state in South Africa. Officials estimated 100,000 people lined up to file past his casket in Pretoria, but up to a third of them had to be turned away. Police struggled to maintain order, and some in the angry crowd broke through the barriers. Mandela's state funeral is set for Sunday in Qunu.

The U.S. Senate spent its second straight night in all-night session, extending its continuous working streak since Wednesday. Shortly after 7:00 this morning, senators overwhelmingly confirmed Deborah Lee James to be the next secretary of the Air Force. She's the second woman to head up the military branch. Republicans have drawn out debates on presidential nominees in retaliation for new Senate rules that limit the useof filibusters.

The date is set for President Obama to deliver his 2014 State of the Union address to Congress: January 28. Speaker of the House John Boehner sent the invitation today, and the White House quickly accepted.

Stocks rose slightly on Wall Street today, as investors remained cautious ahead of next week's Federal Reserve policy meeting. The Dow Jones industrial average gained nearly 16 points to close at 15,755. The Nasdaq rose more than two points to close just below 4,001. For the week, both the Dow and the Nasdaq fell roughly 1.5 percent.