Hundreds of people showed up at an "anti-hate" rally in downtown Denver and observed a moment of silence in memory of an African immigrant allegedly gunned down by a skinhead because he was black. Oumar Dia, a 38-year-old refugee from Mauritania, was killed Nov. 18 after leaving his job at a downtown hotel just before midnight. The killing was the latest in a rash of violent incidents linked to skinheads in the Denver area. A woman who had tried to help Dia was also shot, and the rally heard a message she taped from her hospital bed. Nathan Thill, 19, admitted killing Dia.