(Newberg, OR)  --  Two students are in custody after being accused of planning to attack fellow students and staff at Newberg High School.  Police say the suspects tried to get a gun and other weapons for a threat of violence against students and staff members.  Yamhill County prosecutors say it's likely that charges will be filed against only one of the students, a 17-year-old who's being held on a probation violation.  District Attorney Brad Berry says the plan, if carried out, would have resulted in many casualties.