That's 30 minutes of my life I'll never get back.
The guy's basic science is sound, but his analysis of the audio files is full of crap. He's trying to use audio files taken by many different people from very different locations using very different devices, and analyse them as if they all were taken from the middle of the venue. He hasn't taken into account the variable fire rate inevitable when using a bump fire stock, and he has not tried to make any echo analysis.
If you look at the area where the shooting took place, there are three hotel buildings surrounding the shooting venue that will create very strong echoes; the Tropicana, the Excalibur, and the MGM Grand.
Dr. Greer is full of it.