This note is in response to your invitation for medical professionals to comment on the LV shootings with respect to the authenticity of the publicly available videos and whether they prove or disprove that actual victims were injured or killed. I am a retired surgeon with experience in managing patients with massive blood loss in an operating room setting and in other in-hospital cases of marked hemodynamic instability from hemorrhage.
The retired surgeon from Florida made many excellent points already and I will try not to repeat them. Here are some additional problems with the scene as presented in the publicly available videos:
1.) We do not see CPR being conducted on anyone that I am aware of. This would be extremely unusual for a massive shooting. Surely someone would have captured it on their cell phone. Even if it took a while for the EMT's to arrive, it would be reasonable for non-medical personnel in the audience who have taken a basic CPR course to have started it.
2.) Given the alleged number of victims, we should have seen some evidence of arterial bleeding, no doubt at least several instances of massive hemorrhage (arterial bleeding is often associated with blood being ejected from the site of injury, a so-called arterial "pumper"). What is the probability that no one captured an example of it?