DES MOINES, Iowa (AP) — Authorities say a teen motorcyclist who led police on a high speed chase in Polk County died after crashing the bike. The Iowa State Patrol says the crash happened Thursday afternoon, killing 18-year-old Matthew James Harris, of Mitchellville. Investigators say he sped off when Pleasant Hill police tried to stop him. The patrol says Harris lost control of the bike near an intersection and was thrown from bike, sustaining fatal injuries. Police say was wearing a helmet at the time of the crash.