Some people have said that, immediately after the burst at the :03 second mark, you can here fire from another gun in the distance. I think that sound is much more likely just the echo of the “close” shots you can hear at :03.
The burst at the :45 second mark sound, to me, to be in a different location than the :03 burst.
That difference is highlighted when you hear the “close” shots again at 1:09.
He might have had suppressors on one or two of the weapons. Might the difference in caliber produce a variance as well?
He had 23 different rifles, according to the Daily Mail.