Police officers do have more authority to point guns at people than the general public, but this varies from state to state. Would that officer be charge with a crime? Probably not, as nobody suffered any injury. He would, however, be subject to internal sanction, and could very well lose his job.
Police officers are given more leeway in pointing guns at people because we have to deal with situations that ordinary folks are expected to walk away from, and it's sometimes better to be safe than sorry. In the scenario AFARR mentioned the officer definitely shouldn't have drawn his gun, given only the facts listed, but I seriously doubt he would be charged with a crime. Days off or termination, but not criminal charges.
And believe it or not, you can hide a .22 derringer or some .22 or .25 autos in a Speedo. People have hidden such things up their rectum, under large breasts, etc, so you can NEVER make the assumption that there is no way a person can be armed until you've searched (and no, body cavity searches are not standard, for those of you who will follow the above too far).