article_snippet: A team of black-clad marksmen march across the airport tarmac, while a sea of police outriders rumble through downtown Los Angeles.
article_snippet: Is America mobilising for a major emergency?
article_snippet: Scroll down for video .
article_snippet: Men in black: A sniper team cross the airport tarmac as Obama arrives in LA to appear on host Jimmy Kimmel live .
highlights_snippet: Snipers spotted at LA before Obama landed in Air Force One .
  