Kim Gi-jong, the 55-year-old man who attacked US Ambassador Mark Lippert on Thursday morning, is the head of Urimadang Dokdo Keepers, a left-wing civic group.
Kim, who assailed Lippert during a meeting in Seoul, admitted that he conducted the attack to protest the ongoing South Korea-US military drills that began earlier this week. He was arrested at the scene.
Kim was a member of the Korean Council for Reconciliation and Cooperation, the civic group that had invited Lippert to its morning conference Thursday.
In 2010, he was reportedly arrested on charges of throwing blocks of concrete toward then-Japanese Ambassador Toshinori Shigeie during his lecture in Seoul. He was given a two-year jail term suspended for three years.
Kim has been engaged in a series of campaigns, including one to safeguard Korea's easternmost islets of Dokdo.
In 2006 after Japan's Shimane prefecture declared its Takeshima Day, after the Japanese name for Dokdo, Kim, along with other activists, changed their home addresses to one located on the islets.
In 2007, Kim set himself on fire during a one-man protest in front of Cheong Wa Dae, calling on the government to thoroughly probe a case in which a member of his civic group was attacked by unidentified men at the group's office in Seoul.