NEW : One man , 47 , is being held in Arnold 's case in Montana , a police chief says . NEW : The second male , age 22 , has been `` detained for questioning '' in Rapid City , South Dakota , added DiFonzo . Another man , six days ago , is being `` detained for questioning '' in Montana , he says . Sherry Arnold was a teacher with the Sidney Public Schools in eastern North Dakota . She had last been seen six days ago out on 9:30 a.m. run .
NEW : One man , 47 , is being held in Arnold 's case in Montana , a police chief says . NEW : Another man , six days ago , is being `` detained for questioning '' in Montana , he says . Sherry Arnold was a teacher with the Sidney Public Schools in eastern North Dakota . She had last been seen six days ago out on 9:30 a.m. run .