A search warrant says the 16-year-old suspect in a mass stabbing at a Pennsylvania high school wrote a document that dealt with a Norse end-of-the-world legend.

The warrant was unsealed Tuesday in the case of Alex Hribal (RY'-bal), of Murrysville.

The former Franklin Regional High School sophomore is jailed on charges he stabbed 20 fellow students and a school security guard on April 9 using two knives he brought from his kitchen.

Hribal's attorney didn't immediately return a request for comment on the warrant, which was first reported by The Pittsburgh Tribune-Review. Investigators are seeking Hribal's cellphone records so they can see what websites he visited.

The warrant says Hribal wrote about "Ragnorok" — a "Norse legend about the end of the world" — and "describes his dissatisfaction with school and society."