Thank you all for your responses.
We evaluated the possible cause and isolated all loads before we reset the main breaker. We had an outside contractor with 30cal suit reset the breaker to keep everyone happy. We then turned on the unrelated breakers to the suspected cause. Suspected Load: A motor control center feeder breaker had also tripped with the mains and there was a report of a BANG when a pump was started. Then we investigated and found that the Motor Control Center bucket for the pump had melted its buss clips and damaged the buss. Hard to tell if it flashed to ground or phase to phase.
