The FBI today revealed that the return address on the bomb that killed a Madison Avenue executive Sunday named an H.C. Wickel at the Department of Economics, San Francisco State University. However, FBI agents tell TIME San Francisco bureau chief David Jackson "there is not now nor has there ever been an H.C. Wickel -- neither as a professor or as a student at the university." FBI agents also say that 40 percent of the 3,100 calls they've received from the public in connection with the bombing refer to a man resembling the composite sketch they've released. The drawing portrays the killer as a white man in his 30s or 40s. Investigators tell Jackson that the case will be solved only with help from the public. "Clearly they are stumped and are no closer than last year to solving this," Jackson says.