The 16-year-old boy who killed three children and a teacher , injuring two other people, at a school in Bend, Oregon, was assaulted twice in recent years, once while he was trying to defend his mother, police records show.

In one incident, he told his sister he had been bullied at school, according to police, who wrote that he “likely had a cognitive disability.”

Griffin John II opened fire on a special-needs classroom at Silver Rail Elementary School on Oct. 15 before he was killed by a man who has two daughters at the school .

Much about John remains unknown, and law enforcement is still investigating him and any potential motive.…