I am not expert in tactics,training or medicine but I do have some ideas.
Police departments are woefully undertrained usually because of budget limitations.
I think the Miami shootout and the L A Bank robbery illustrate the same point. The good guys were outgunned.
At the risk of being impeached let me state that the 9mm is not a good pistol round for anti-personnel use.Its place is in a full auto submachine gun where it can be dispensed by the pound.
The reason that most 9mm police shootings involve many many rounds is that it requires many many rounds.
A .45ACP JHP would be a much better choice but public opinion opposses its use because it might hurt somebody.
Marksmanship training would help in the use of any caliber but its not goung to solve the problem bt itself.
Better days to be,