LAS VEGAS (AP) — A teenager arrested last week with an unloaded assault rifle at a Las Vegas high school has been linked by counterterrorism investigators to another local teen who federal authorities said stockpiled guns and explosives and spoke about staging a mass casualty attack.

Police already were looking for 18-year-old Jake Benton Howell when he arrived at his former school on Dec. 21 with 40 rounds of ammunition and a 7.62mm SKS rifle in the back seat of his car, according to a police report released Thursday.