DeafSA, South Africa's leading deaf association, condemned the presence of the unknown man at the memorial, which was attended by President Jacob Zuma and scores of world leaders including U.S. President Barack Obama.
 
While dignitaries were addressing the crowd in the 95,000-seat Soccer City stadium, the young, suited man with an official security pass around his neck produced a series of hand signals that experts said meant absolutely nothing.
 
Besides the bizarre twist to an event that also saw Zuma booed and jeered, his presence on the stage within yards of Obama and Brazil's Dilma Rousseff raises awkward security questions.