The massacre of 10 foreign climbers on Pakistan's "Killer Mountain" a year ago came after a failed attempt to capture a Chinese-American to use him as a high-value bargaining chip, officials and militant sources have said.
The June 22, 2013 attack at the base camp for the 8,126-metre Nanga Parbat, Pakistan's second-highest mountain, was the deadliest assault on foreigners in the country for a decade.
One year on, with tourism in the northern Gilgit-Baltistan region still suffering, most of the 10 suspects implicated in the attack are still at large, while sources close to the investigation have cast doubt on the guilt of some of those arrested.
The victims were identified as three Ukrainians, two Chinese - including Chinese-American Chen Honglu - two Slovakians, one Lithuanian and one Nepalese as well as a Pakistani guide.
But dual national Chen was the prime target, according to militant sources.
The story begins in early June 2013, when a local jihadist contacted other fighters to tell them two mysterious commanders had arrived from out of town and wanted to meet.
The men met at a house in the town of Chilas, where the two strangers, wearing all-enveloping burqas, were introduced as important Taliban cadres from Afghanistan.
The local fighters were briefed on the planned Nanga Parbat operation. "They were told that the mission was about kidnapping a foreigner in order to later bargain for the release of an important Taliban commander," an investigator assigned to the case said.
Militant sources said Chen was the specific target, with the plan being to trade him for Taliban in Afghanistan.
The men then met a local sectarian group in a forest, recruiting two more fighters - against the sectarian group leader's wishes - to bring their number to 10.
They left for the Nanga Parbat base camp in the early evening, wearing the uniforms of the Gilgit Scouts, a paramilitary police unit.
"The two commanders had taken off their burqas and were in military uniforms like the rest of us but their faces were covered with a cloth," a militant source said, explaining that they were supposed to grab the target.
But as the attack unfolded in the freezing night, Chen burst out of his tent and tackled one of the militants using martial arts skills.
The militant, named Mujeeb, panicked and shot him, destroying the main purpose of the mission and infuriating the shadowy masked commanders.
The remaining climbers were then tied up and shot one by one.