The catch is that of those 15,000 police killings, many of them are determined to be justified. The data says so. The only data there is says so. There is no other data. There can be no other data. To ask for data is false.
Now what if some of them that are determined to be justified really were not justified. Fox and hen-house. You say you want data about that but that is ridiculous - the data says they were all justified.
This is one of the main reasons for the very existence of BLM.
The noise you hear and the riots you see are about the most egregious cases - the ones chosen to make noise about.
Also, of course these questionable cases are NOT representative of what happens in the remainder of the 15,000 cases. Nobody has ever said that.
No, that's not true. Nothing is preventing someone from researching every single instance of police killing in the line of duty. Sure, to collect those data would be difficult, and inconvenient, and time-consuming - possibly even expensive. But it's not impossible; it can be done.