Police are individuals with their own thoughts and ideals.
Yet they claim to honor an oath to uphold the constitution
Funny how that works
Anyone can claim anything.
This works both ways. They claim to uphold the law (generally only higher ranking officials swear to uphold the constitution), but it is also possible that others can claim the police violated their rights.
All police officers must swear to uphold the law, but there is really not a very good vetting process for potential officers so we will see a lot of bad officers. Plus the fact that police officers are given a lot of perverse incentives to make additional arrests and charge citizens with additional crimes that may not hold up in court.