Today in Pictures: Dec. 18, 2012

A Pakistani mother mourns beside the body of her daughter, who was killed while on the job as a polio vaccination worker, at a hospital following an attack by gunmen in Karachi, Dec. 18, 2012. Gunmen on motorbikes shot dead five female Pakistani polio vaccination workers, police said, highlighting resistance to the country's immunization campaign. (Rizwan Tabassum/AFP/Getty Images)