Guards guilty of killing 14 Iraqis in a square in Baghdad in 2007.
Julia Pierson steps down following several high-profile security lapses.
Suspect had 800 rounds of ammunition and a machete in his car.
President Obama has ruled out a combat mission in Iraq.
Ceremonies marking 13 years since attack held in New York, Washington.
President Obama to set out "game plan" in speech Wednesday.
Two men were convicted of raping, murdering 11-year-old girl.
The magnitude-6.0 quake is thought to be the strongest in 25 years.
A physician with Doctors Without Borders who returned to New York City after treating Ebola victims in West Africa tested positive for the virus on Thursday, setting off fresh fears about the spread of the disease.
Helmed paper during Watergate scandal that toppled President Nixon.
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