Two teenagers from Nassau County are dead after a crash on the Northern State Parkway Thursday.Cops say Giacomo Alfieri was in a 2007 BMW that was speeding and smashed into a tree-lined median between exits 41 and 42. The car was going so fast, officials say, car parts were scattered across both directions of the parkway. Officials say Alfieri and Michael Moniz, his passenger, were both ejected from the vehicle and pronounced dead at the sceneThe victims were both in their senior year at John F. Kennedy High School in Bellmore. The school says it has set up a crisis center for students and staff members.First responders say it's one of the worst accidents they have seen.