Because the conduct witnessed by the police officer reasonably led him to believe that an armed robbery was in prospect, he was as reasonably led to believe that the men were armed and probably dangerous and that his safety required a “frisk.” Because the object of the “frisk” is the discovery of dangerous weapons, “it must therefore be confined in scope to an intrusion reasonably designed to discover guns, knives, clubs, or other hidden instruments for the assault of the police officer.”
