The $451 million mystery is over.A 20-year-old Florida man claimed the fourth-largest jackpot in Mega Millions lottery history, lotto officials confirmed.Shane Missler, of Port Richey, was the lone winner of the Jan. 5 jackpot. He elected to take a lump sum payout of $281.2 million, officials said.Missler plans on pursuing a "variety of passions," according to the Florida lottery, as well as helping others.