Convenient timing? North Korea has detained an American tourist for "rash behavior," state media reported Saturday, as President Obama arrived in rival South Korea. The 24-year-old, identified as Miller Matthew Todd by the official Korean Central News Agency, is reportedly being held in custody after allegedly tearing up his visa, saying he would seek asylum and "shelter" in the North. Todd's detainment comes as Obama and South Korea threatened tougher sanctions against North Korea if it carries out an anticipated fourth nuclear test. An 85-year-old American tourist has also been held captive in the country since 2012.