Citing a lack of evidence, the Los Angeles County district attorney's office announced that no criminal charges will be filed against Pomona Mayor Donna Smith for allegedly using a shotgun last month to threaten an 18-year-old college student who had parked his car in front of her home. Deputy Dist. Atty. Candace Beason said the case boiled down to Smith's version of events against that of Eric Johnson, the Cal Poly Pomona sophomore who complained that the mayor pointed a gun at him and falsely accused him of buying drugs after he dropped off a friend Aug. 15. Smith, who has complained frequently about gang activity and drug trafficking in her neighborhood, said she held the shotgun at her side in self-defense.