San Antonio Express-News music critic and syndicated columnist Raviro Burr has resigned — as the newspaper’s own investigation was concluding into allegations that he hired another writer to produce more than 100 stories since 2001. Burr’s letter of resignation called it a “difficult situation” — “ “I may have been a little overzealous, or overreached in trying to be the best reporter/syndicated columnist I could be,” he said. “I sincerely apologize for breaking any rules.”