(CNN) -- The Navy was unaware until after the killings at the Washington Navy Yard that gunman Aaron Alexis had been arrested in 2004 for shooting out the tires on a vehicle and claiming he had blacked out in anger, a senior Navy official told reporters Monday.

WASHINGTON (CNN) -- President Barack Obama said Sunday that the United States "can't accept" last week's killing of 12 people at Washington's Navy Yard as "inevitable," but the shooting should instead "lead to some sort of transformation" on gun violence in the United States.

NEW YORK (CNN) -- A Columbia University professor who wrote about hate crimes against Sikhs may have become a victim of one himself when 12 to 15 people attacked him while shouting anti-Muslim slurs, police said.

(CNN) -- The weekend massacre at an upscale shopping center in Kenya is shining a new light on an old concern for Western counterterrorism officials: the recruitment of jihadist fighters from Somali communities in the United States, Canada, and Europe.

Congress always works on two tracks. The first rail is legislation that gives the government authority to spend money. The second rail is one that actually appropriates the funds.

Guns don't make a nation safer.That's the conclusion of a study that found a strong correlation between gun ownership rates and the risk of death by firearms in more than a dozen developed countries.

The Environmental Protection Agency is proposing new rules aimed at limiting the amount of carbon pollution coming from new power plants.

House Republicans are threatening to shut down the government unless the budget bill defunds Obamacare. The battle is certain to fail since the Senate lacks votes to kill health care and the president would veto any bill that did pass. 

A class of Connecticut seventh-graders were called the n-word and threatened during a nighttime slavery re-enactment field trip 

Oilfield services giant Halliburton pleaded guilty Thursday to destroying test results that investigators had sought as evidence in the 2010 Deepwater Horizon oil spill. The spill, just miles off the Louisiana coast killed 11 people, countless sea creatures and hurt the environment.