Arterial blood is bright red. Very bright red. Hemoglobin is the protein which binds oxygen for transport and is responsible for our blood being red.
Veinous blood, which tends to circulate on the outer and exposed areas of the body, is a very deep maroon, having been stripped of oxygen and carrying CO2.
Did no one pay attention in health class? Or during first aid/triage training?
You'd be amazed at how much blood is in a person, and how so little blood can appear to be massive amounts.
I am not saying you are wrong, per se, - but I am not of the opinion that "it's all just fake! Nothing really happened."
I can almost guarantee that if something like this were to happen near me, there would be people saying the same things… "Look! It's fake!" - because people have come to doubt the media to such a degree that they refuse to believe any event as being real.
There wouldn't be a need for MK_Ultra psycho-assassins if there was the ability to create, so easily, such broad conspiracies of mass shootings that are all smoke and mirrors. The belief all of it is fake displaces further analysis into the shooter and local authorities.