That second group of shots sounds completely different.
Listen to the first three. Crack thump Crack thump, Crack thump.
OK. I can believe that was an AR-15 from 125 yards away.
But then the next 5-6 shots......WTF was that? Sounded like a completely different weapon. The echo sounded very different (indicating it was taken from a different range) also.
Then a second or two later shot #9 which was the police/SS counter sniper.
Yes completely different sound. Besides that sound difference:
1. Interval between shots in first group of three is maybe three times longer than the interval between shots in second group. To me, that indicates a different shooter using a different weapon. The shooter of the second group of shots is more experienced and can keep rifle aim on target more proficiently than first shooter. Does the second weapon have less recoil, less lift, and faster action?
2. The big difference in echoes. The first shooter has a large, acoustically hard, vertical surface behind him. The second shooter does not have such a surface behind or nearby and might be indoors.