Walking home Friday evening, at the corner of Montgomery and Second St., in San Francisco, I winessed train passengers rushing out of the underground train station. Police were rushing in. Someone had heard a "pop."

It was nothing.

The panic has spread to small towns:

And a plane headed to San Francisco was diverted because three men "suspiciously" swapped seats with each other:

The flight landed at Kansas City International Airport around 7:50 a.m. The flight crew made the decision to divert the flight when several passengers did not follow takeoff instructions and continued to display suspicious behavior during the flight.