TUCSON — A victim of the shooting spree here that severely injured Rep. Gabrielle Giffords was taken into custody on Saturday after the police and witnesses said the man spoke threateningly at a televised forum intended to help this stricken city heal. Eric Fuller, 63, a military veteran who was passionate about liberal causes and who had supported Ms. Giffords, was “involuntarily committed for mental health evaluation,” according to Jason Ogan, a spokesman for the Pima County Sheriff’s office. Mr. Fuller, who was shot in the left knee and the back on Jan. 8, was among several victims, medical personnel...