BROOKFIELD, Wis. (AP) – A Bureau of Alcohol, Tobacco, Firearms and Explosives agent says it is tracing one weapon used in the fatal spa shooting in a Milwaukee suburb.   Agent Tom Ahern tells The Associated Press it’s a .40-caliber semiautomatic handgun. He says any additional information will have to come from the Brookfield police, who are investigating Sunday’s shooting, after the trace is completed and the results provided to them.  Three women were shot and killed and four injured at the Azana Day Spa in Brookfield. Their identities have not been released.  Police say the suspect, 45-year-old Radcliffe Franklin Haughton, was found dead of a self-inflicted gunshot wound.   Haughton’s wife worked at the spa. It is not known if she was one of the victims.