MIAMI (AP) - A 20-year-old college student who told investigators he was merely trying to get a reaction from President Barack Obama's supporters pleaded guilty Wednesday to posting threatening messages against the president on Facebook. Joaquin Amador Serrapio Jr. could get up to five years in federal prison for pleading guilty to a single count of threatening to kill or harm the president, but likely will get less time, said his attorney Alan Ross. Sentencing is set for Aug. 22 before U.S. District Judge Marcia Cooke.