SAN FRANCISCO (AP) - City officials here have opened an investigation into why authorities apparently ignored numerous complaints about a full-scale drug den being operated out of the apartment of an elderly woman who suffered from dementia. Six alleged gang members took over the 84-year-old woman's apartment for months, even eating her free senior meals, police said after their arrests last week. The woman's second-floor apartment in the city's Mission District was littered with drugs and crack pipes. "This is one of the most egregious cases of elder abuse that I have ever seen," Trent Rhorer, executive director of the...