Sounded like a belt fed M60 or other squad automatic weapon (SAW). It took him 30 seconds in between firing to reload the weapon as a possibility. This means he did not have the belts linked together. He would fire a few hundred rounds and load another belt. A picture of a bullet hole in a metal building was not from a 5.56 round. It was large and appeared to be from a 7.62 (.30 caliber) round. Could also have been a 7.62x54R Russian PKM 200 round belt fed weapon.
This man was pure evil. How do you stop such evil other than through prayer and help from God?