Police arrested a 52-year-old man suspected of killing his 78-year-old mother Friday morning in Lake Oswego. Virginia Brix of Redmond, Washington, was found dead inside a home in the 17000 block of Mardee Avenue after police arrived to do a welfare check at 8:40 a.m., authorities said. She had been appointed her son’s guardian two years ago after his mental health seriously deteriorated and he was suffering escalating delusions, according to court records.