You're not bulletproof...

Armed Citizen…(27)

A man entered Smith’s Marketplace one afternoon and purchased a knife. Police say the man then used the knife as a weapon and attacked several people. One victim was stabbed in the abdomen while another was stabbed in the head and arms. All the while, the knife-wielding assailant had been yelling at his victims that they had “killed his people.” Before he was able to locate another target, a citizen with a concealed firearm intervened. The man with the knife was told to drop his weapon or be shot. He complied and was detained until police arrived. (ABC4, Salt Lake City, UT, 4/27/12)

http://www.nrapublications.org/index.php/armed-citizen/