The Tulalip tribe, of which Fryberg was an active member, issues a statement (full text here):
The Tulalip Tribes denounce the horrific actions of Jaylen Fryberg, who took the lives of two of his classmates and grievously injured three others. All of the young people he attacked were his friends, and two were his cousins. Parents and children alike are struggling to understand what caused him to act in such a manner. Even though we may never know why, there can be no justification for taking the lives of others. These were the acts of an individual, not a family, not a tribe.