A white former policeman laughed as he walked along a downtown Pretoria street, casually shooting to death six blacks and wounding 16, witnesses said Wednesday.

Three of the people injured Tuesday in Pretoria died in a hospital overnight, raising the death toll to four men and two women, police said. The gunman, identified as Barend Strydom, 23, surrendered to two black police officers after the shooting spree.Police said he had resigned in February after an internal investigation found him guilty of "improper behavior" that included "possession of radical right-wing documents." Minister of Law and Order Adriaan Vlok said Strydom is a member of the neo-Nazi Afrikaner Resistance Movement.