Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: Photos of US ambassador to South Korea Mark Lippert meeting with the country's leaders have emerged for the first time since the envoy was attacked by a knife-wielding pro-North Korean activist. Lippert is recovering at Severance Hospital in Seoul, and was able to meet with US Navy Admiral James Winnefeld as well as members of South Korea's ruling and opposition parties. Police are charging the activist, Kim Ki-jong, 55, with murder after he slashed the ambassador while screaming demands for Korean reunification. The attack Thursday on Lippert, at a forum about reunification, prompted rival North Korea to gloat about 'knife slashes of justice,' that left deep gashes and damaged the ambassador's tendons and nerves.Ambassador Mark Lippert injured in a surprise attack at a breakfast meetingKim Ki-jong, a 55-year-old anti-US activist, was immediately arrestedPolice seeking three charges in attack, including attempted murderDoubts over whether he carried out attack alone or was part of conspiracyKim has visited North Korea several times and had books from the countryLippert needed 80 stitches for slash to his face and may have nerve damageHe could be discharged from hospital Wednesday after stitches removed 
 Question:_ is well-known among police and activists as one of a hard-core group of protesters willing to use violence to highlight their causes.

Kim Ki-jong