From Wikipedia —

  "Earthquake light is an unusual luminous aerial phenomenon
  that reportedly appears in the sky at or near areas of
  tectonic stress, seismic activity, or volcanic eruptions."

http://en.wikipedia.org/wiki/Earthquake_light

Considering there were reports of seismic activity in the area around the approximate time of the event, it's possible that ionized air promoted formation of sprites and/or ball lightning.