Associated Press photographer Anja Niedringhaus was killed today, shot to death by an Afghan policeman while covering the upcoming national election. She covered conflicts from Bosnia to Afghanistan for more than 20 years, earning a Pulitzer Prize in 2005, as part of a team of AP photographers covering the Iraq War. Last November I was very happy to be able to feature her amazing work in a photo essay titled "Afghanistan: Seen Through the Lens of Anja Niedringhaus." What I wrote then remains true: Documenting a decades-long story like the Afghanistan War is a challenge for any photojournalist, from simple logistical issues, to serious safety concerns, to the difficulty of keeping the narrative fresh and compelling. Niedringhaus did a remarkable job, telling people's stories with a strong, consistent voice, an amazing eye for light and composition, and a level of compassion that clearly shows through her images. A remarkable voice has been lost today.