A mechanic at a bus depot in downtown San Diego shot a co-worker to death and critically wounded another early Tuesday before being killed by police, authorities said. After finishing his shift around 2 a.m., the Metropolitan Transit System worker walked into a lounge area and shouted "nobody's going to leave" before heading out to a parking lot and firing several shots, police Capt. Jim Collins said. Arriving officers found a dead man on the ground at the facility and the mechanic holding a handgun at his side. He ignored repeated demands to drop the weapon and used his other hand to make a cell phone call, Lt. Kevin Rooney said. "When the call ended, he started to raise the gun at the officers and they shot him," Rooney said.