I've never heard of them fired by police. It would have been very newsworthy, I'd think, for exactly the reason you suggest and because it would be so unusual. Police in the U.S. rarely have to shoot anybody with any kind of bullet anyway.

Presumably police would use hollow-points against an armed assailant clad in some kind of body armor, or in some situation where the commonly issued bullet might be ineffective. Like shooting a rabid wild animal.

Just as a point of information, American police generally have to justify any use of a firearm in the line of duty, with forms in triplicate. And if there's any doubt that a shooting was justified, they're prosecuted criminally and civilly.