Horner was the chief correspondent for Sveriges Radio's Asia division and had covered multiple stories surrounding the War in Afghanistan (2001–2021), as well as natural disasters.

[6] During his career, he covered stories including the decline of the Taliban, the 2004 Indian Ocean earthquake and tsunami, and the Fukushima disaster.

[4] He acknowledged the danger he was sometimes in when he spoke in 2011 to a co-worker at Swedish Radio about his decision to stay on the front lines of the Fukushima Daiichi nuclear disaster: "Most journalists are not interested in risking their lives for a story.

While on his way to investigate the story, two men shot Horner execution style in the middle of a street in the Wazir Akbar Khan, Kabul district.

[5] Two months before Horner's death, the Taliban had attacked the same Lebanese restaurant Taverna du Liban, which was a popular spot for "westerners.

"[13] Director of Swedish Radio Cilla Benkö followed with similar remarks saying, "It is shameful that so little is done to safeguard the working conditions of journalists.

Unesco’s report indicates that, especially in the Arab world and many countries in Africa, deaths are frighteningly common with a very low rate of solving cases of killed journalists.

Borås Tidning and the Tore G Wärenstam Foundation, as well as the Radio and journalism education programme at the University of Gothenburg, have since awarded one journalist each year that exemplifies Horner's spirit with a cash prize.