point 1 : One of several eyewitnesses.
point 2 : Light travels just slightly faster than sound.
point 3 : You COULD be entirely correct."
On point 2, let's see (from physics class): light travels at 386,000mph and sound (in air) at 1000 feet/second or about 300mph. Thus, light goes nearly instantly over these eye-witness distance while the sound takes about 5 seconds per mile. Easily one could see an exploision/fire prior to hearing it.
Not quite. 1000 feet/second is 60,000 feet/minute. There are 5,280 feet in a mile. Rounding it down to 5,000, sound would be 12 miles/minute. Multiply that by 60 minutes and you get 720 miles/hour (not 300mph).