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The photo taken last December of a man assassinating Russia's ambassador to Turkey was named World Press Photo of the Year on Monday.
Associated Press photographer Burhan Ozbilici took the photo. He was immediately asked to tell its story.
Ozbilici said he took the photo because he needed to "represent good journalism."
Ozbilici's photos quickly made their way around the world.
He said he thought something interesting might happen at the art exhibition in Ankara, Turkey. So, he went to the event at the last minute and brought his camera.
Mevlut Mert Altintas killed ambassador Andrei Karlov and shouted "Don't forget Aleppo! Don't forget Syria!" Altintas opposed Russia's involvement in the Syrian civil war.
Ozbilici said he moved to a safe place in the gallery and took his photos because he would not have had a good answer if people asked him later: "Why didn't you take pictures?"
Many people praised Ozbilici's bravery.
Stuart Franklin is the photo competition's top judge. He said the photos were, in his words, "terrific" and Ozbilici "had extraordinary composure in being able to sort of calm himself down in the middle of the fray and take the commanding pictures that he took."
Franklin thought the photo was good, but in an opinion article published by The Guardian, he said he voted against naming the photo as the best of the year.
He wrote that the photo showing a murder was "problematic," and he did not think a terrorist's message should be "amplified" by awarding a prize for the photo. Franklin said other photos in the competition better served humanity.
While Ozbilici's photo was the press photo of the year, others received prizes, too. Photographers won awards in many categories, including: Contemporary Issues, Daily Life, Nature, People, Sports and Long-Term Projects.
Jonathan Bachman of the Reuters news service won the Contemporary Issues category for his photo of Ieshia Evans being detained by police in Louisiana during a protest over the shooting death of an African-American man.
Evans was wearing a long dress and not resisting as officers ran up to her with plastic handcuffs.
Franklin said Bachman's photo was "an unforgettable sort of comment on passive resistance. It's really a lovely photograph. You'll never forget it."
Other award-winning photos show problems around the world. For example, the winning nature photo by Brent Stirton was a reminder of how endangered species are threatened by poachers. The photo showed a dead rhino, killed for its horn, in a game preserve in South Africa.
Another image showed a Cuban woman in a taxi days after the death of Fidel Castro. It was part of a series of winning photos in the "Daily Life" category by freelance photographer Tomas Munita. He documented the changes in Cuba as the country moved to normalize relations with the United States.
You can see more winning images at worldpressphoto.org and by following WorldPressPhoto on Twitter.
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I'm Dan Friedell.