"One of those injured was Delores Werling, a 70-year-old, part-time teacher of the handicapped who lives on a 200-acre farmstead northeast of Tipton, Iowa, about 37 miles southeast of Cedar Rapids. Her husband, Bryce Werling, who is a retired farmer, said Saturday in an interview that he and his wife drove up to their mailbox about 11:20 a.m. Friday. His wife, sitting on the passenger side, opened the mail box, took out some mail and, noticing an object, asked her husband if he had left something in the mailbox." Yet another incident where the mail was in the box, along with the bomb.
Five more bombs found in mailboxes
Like I said, the only reasonable explanation I could think of...
Good catch. I don't think the mail person was paying attention while on route. My explanation has now been debunked, but I don't mind, when more evidence is presented.