It's important to take into account witness statements. There are issues at play such as whether the uniform is clearly identifiable and marked. The other side is the lighting conditions and positioning of the security guard/suspect and responding officers and whether such, if any, marking were identifiable to them. A note on uniforms. For example, when I type my reports while on routine patrol, I will state I am working in full uniform and driving a marked police vehicle. That is different when, for example, I am serving a search warrant and am not wearing a full uniform. There I will notate that I am wearing a modified tactical uniform which clearly state police in large bold white print on the front and back. The point here is in how the courts address search and seizure. Lawful commands from a clearly marked law enforcement officer is hard to negate when they are in full uniform. It alleviates any issues of uncertainty or taint. To draw back to the point at the top of the page, I would need to see what entails a uniform and whether it's clearly identifiable. Again, officers are responding - with lights and siren - to a chaotic and ongoing scene where an active shooter is reported. Radios are loud, sirens are loud, driving to scene with a hot call causes a massive adrenaline rush. Hot calls will involve a multitude of duplicate 911 calls reporting varying information. There is a lot to dissect here.