I think he told them on his radio what was going on and told them to call 911.
Everything I have seen and read about both the security guard and the building engineer only mentioned radio conversations. I am not sure they had phones with them and they may not have been able to or authorized to just call 911 without someone else making that decision, making that call.
That may be what caused the delay- getting the right person to authorize calling 911. That can happen if the place has their own security or their own police department; they do not normally call actual law enforcement, so there can be a delay when they need to.
It is hard to tell what the truth is, but if the MB didn’t call the police when their security guard was shot then the LVMPD actually responded pretty fast.
The other issue is the MB knew exactly what room the shooter was from their security guard and building engineer; yet the story is the LVMPD had no idea where the shooter was and had to figure it out when they arrived. If true that wasted a lot of valuable time while people were being shot.
I cant find the audio at the moment - but I swear - at least one version of the “Engineer’s” call - you can hear the person they are talking to - and they seem aware of the situation - and says something like “he’s on 32” - as if they are talking to someone else.