U.S. Ambassador to South Korea Mark Lippert (3rd L) leaves after he was slashed in the face by an unidentified assailant at a public forum in central Seoul March 5, 2015. Lippert was attending a breakfast forum in central Seoul when a man attacked him, slashing him in the face, a witness at the event told media sources. (Yonhap)

Security personnel detain an unidentified assailant who attacked the U.S. ambassador to South Korea Mark Lippert at a public forum, in central Seoul March 5, 2015. The U.S. ambassador to South Korea was slashed in the face by an unidentified assailant at a public forum in the capital early on Thursday, police and a witness said. Ambassador Mark Lippert was attending a breakfast forum in central Seoul when a man attacked him, slashing him in the face, a witness at the event told media sources.

A suspect, center bottom, identified by police as 55-year-old Kim Ki-jong, is detained by police officers in Seoul, South Korea, Thursday, March 5, 2015. U.S. Ambassador Mark Lippert was slashed on the face and wrist by a man wielding a knife with a 10-inch blade and screaming that the rival Koreas should be unified, South Korean police said Thursday. (AP Photo/Yonhap, Kim Ju-Sung)

Police officers investigate the table where U.S. Ambassador to South Korea Mark Lippert sat at a lecture hall in Seoul, South Korea, Thursday, March 5, 2015. Lippert was slashed on the face and wrist by a man wielding a blade and screaming that the rival Koreas should be unified, South Korean police said Thursday. (AP Photo/Yonhap, Kim Ju-sung)