JACKSONVILLE, Fla. (KABC) -- A Florida man dressed up as Darth Vader failed to rob a convenience store on Sunday after a hero clerk took action.Police said the suspect, identified as Jacob Mercer, threatened the store clerk with a gun and demanded money when the employee hit him with a jar of ranch dressing.After Mercer left the store, the suspect removed his mask and was identified by a witness.He was later charged with armed robbery and possession of a firearm by a convicted felon.