This is an interesting video interviewing a firearms experts who has been asked by the police to investigate the shooting. He said a gun classified as a "prop gun" has been modified so it can't load cartridges with bullets, only blanks. so the question he has is if the gun was a legitimate prop gun or if they were using a gun that wasn't modified.
https://www.cnn.com/videos/entertain...ad-vpx-new.cnn