LOS ANGELES—Missing California college student Kristin Smart was killed in 1996 during an attempted rape by a fellow student and the suspect’s father helped hide her body, the San Luis Obispo County district attorney said Wednesday. Prosecutors filed a first-degree murder charge against Paul Flores and an accessory after murder charge against his father, Ruben Flores, for helping him conceal Smart’s body, which has never been found, District Attorney Dan Dow said. The two were arrested Tuesday after years of investigations and searches that recently led to evidence connected to Smart’s killing. Smart, 19, of Stockton, was last seen May 25, 1996, while returning to her dorm at California Polytechnic State University campus in San Luis Obispo after an off-campus party. She was inebriated at the time and Flores, a fellow freshman at the school, had offered to walk her home. Flores killed Smart in his dorm room, Dow said. …