An Orem. Utah, teenager accused of stabbing five other students told police after the attack that he's had suicidal and harmful thoughts since he was very young.

Investigators say in a search warrant unsealed Monday that the 16-year-old arrived to Mountain View High School on Nov. 15 with five knives and long wooden sticks with the intent to harm classmates. He went to the locker room because that is where he found a large group of students. The victims survived.

The teen told detectives he used his cellphone and tablet and his mother's computer to look on YouTube to plan the attack and "communicate" his plan. The document doesn't elaborate.

The teen has been charged as a juvenile with attempted murder. The Associated Press is not identifying him because of his age. His attorney couldn't immediately be reached.