An explosion rocked a post office in the western Chicago suburb of Westmont. A man who went into a nearby fire station and said he was responsible was arrested a short time later. He was identified as Robert Ciaciuch, 50, of Chicago. The bomb was placed in the post office's lobby, about 30 feet from its main counter, officials said. Two customers and three employees who were at the counter at the time of the blast escaped injury. Police later defused a second bomb Ciaciuch said he had left in the post office.