An analysis of two sequential burts of gunfire between:
["Taxi Driver Video" the Zapruder Film of the Las Vegas shooting UNCUT / UNEDITED]
https://www.youtube.com/watch?v=mBbOFwWquAw&feature=youtu.be&t=1m7s
and
https://www.youtube.com/watch?v=mBbOFwWquAw&feature=youtu.be&t=1m24s

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T1: Time from start of video (1minute N seconds) at the time of the last shot in the burst.
T2: Time from the start of the video (1minute N seconds) at the time of the echoed sound event corresponding to T1.
TempF: the air temperature (72 degrees F)
FPS:   1130 ft per second -- The speed of sound at 72 degrees F
Elapsed Time:  T2 minus T1, the number of seconds between the last shot, and the echo of the last shot in each burst.
Total Distance:  Elapsed Time * FPS = the total distance traveled between T1 and T2.
Echo Distance  = The distance the echo traveled from the aiming point back to the point of origin.
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Conclusion:  Burst B is NOT two weapons being fired simultaneously.  It is one weapon being fired at a more distant target.  The longer distance, observable in the period between Burst B's T1 and T2, manifests a corresponding longer period of reverb.  It is the reverb that is being incorrectly interpreted as a second weapon (and second shooter) firing at the same time.

Research resources:
https://www.google.com/search?biw=1544&bih=856&q=Forensic+Acoustics+gunfire
http://www.physicsclassroom.com/mmedia/waves/er.cfm
https://www.timeanddate.com/weather/usa/las-vegas/historic
http://www.csgnetwork.com/soundspeedcalc.html