Re: Too late was the cry
The choice of ammunition is not just for the damage done to the target, but for the safety of those around them.
A standard full metal Jacket round will go straight through someone without too much issue, especially in the 9mm-45 Cal range which is were most police issue pistols are going to be.
Hollowpoint rounds by expanding are designed not just to expand to enlarge the wound channel, but also to penetrate the target and stop before exiting. From the shooters point of view you want the round to dump all of it's energy into the target, a round over-penetrating has failed to do this.
The last thing the officer wants is the chance of taking out some poor bystander when the round keeps on trucking, or being unable to shoot when required to for fear of over-penetration allowing the subject to do something people would rather he wouldn't.