OTTAWA — Ottawa police say an 11-year-old boy was arrested after he threatened another student at Eugene Field Elementary School with a knife Friday afternoon. Lt. Adam Weingardner said because of the age of the boy, there will be few details made available concerning the case. Weingardner said school authorities called the school resource officer who conducted the investigation. No one was injured. Although the boy was taken to the juvenile detention center, Weingardner said he doesn’t know if he’s still there.