According to the BPDNewsBlog there was a little bit more than just finding a mocked-up pipe bomb. There was a suspicious individual issuing threats as he left the building, then someone in the office building found the mocked-up pipe bomb.

Right when they solved that, the BPD got hit with some bomb threats.

It does cast some things in a completely new light, like the fact that the city was still on alert loooooooong after they new the Mooninites were a publicity stunt gone awry. Reading between the lines, it looked like the BPD decided to act as if the Lite Brites were part of the problem until they got official confirmation from both Turner and one of the artists that the publicity stunt had nothing to do with the mocked-up pipe bombs.

It's Murphy's Law in action. The shit hit the fan all on the wrong day.