Witnesses claim shooting during protests outside police station was ' a professional job ' by a sniper-style gunman . Both officers were struck by shots believed to come from up to 120 yards away , possibly from a rooftop building . Head of the St Louis Police Association said it suggested the gunman may be someone with weapons experience . two gathered for a candlelight vigil to call for calm and express sympathy for the wounded police officers .
Witnesses claim shooting during protests outside police station was ' a professional job ' by a sniper-style gunman . Both officers were struck by shots believed to come from up to 120 yards away , possibly from a rooftop building . Head of the St Louis Police Association said it suggested the gunman may be someone with weapons experience . Dozens gathered for a candlelight vigil to call for calm and express sympathy for the wounded police officers .