Tyler Jarrell, 18, made up his mind early about life after high school. He wanted a challenge, and he looked to the Marine Corps to provide it.He enlisted on Friday with a training date set for next summer, after graduation. After a flurry of enlistment paperwork over summer break, Jarrell made time for the year’s biggest attraction in his hometown of Columbus - the Ohio State Fair, which opened Wednesday.Jarrell was killed when he was thrown off an amusement ride, the Fire Ball - an “aggressive thrill” carnival ride that swoops like a pendulum and swings in a circle - after a row of seats appeared to smash into a metal structural support beam.