Unfortunately it seems to be more common as of recent. The LAX shooting isn't the only recent one. The Officer Libke who was shot in Oregon at a house fire waited supposedly 90 min and died from his injuries at some point.
http://www.policeone.com/patrol-issu...for-ambulance/
There is an argument to be made for having LEO be trained/certified also as a medical responder, or EMT-B, and I have heard some on the LE side argue for an EMT-T (Tactical EMT basically). You can argue that LE can provide a needed basic level of care or triage if the scene is safe enough, etc. Others tend to argue that "Great, we can stretch the LEO's thinner by having them run EMS calls too!" Then you have some on the EMS side debating how few patient contact hours/experience LEO's would have, and that it would be better to leave it with EMS. Not picking any one side, just sharing the points others keep pointing out to me.
As to my personal opinion. I would like to see LE and EMS work on getting more EMT-B's (as well as I's and P's too) in the first responder network (Fire/Rescue/EMS/LE) and keeping them there. Why? Not just mass shootings, but everyday instances as well, though I don't think that LE need to be medical responders as well. While I do appreciate EMS, I do feel that other first response agencies can provide a needed level of care that perhaps for some reasons, such as scene safety, regular EMS does not. If there is too much resistance from EMS, then perhaps LE should work on creating its own basic medical program similar to what is discussed about the EMT-T.