In most circumstances, police officers do not owe a personal duty to protect specific individuals from harm. The dominant principle comes from the U.S. Supreme Court decision in DeShaney v. Winnebago County Department of Social Services (1989)

Also see: Town of Castle Rock v. Gonzales (2005) Warren v. District of Columbia (1981) Linda R.S. v. Richard D. (1973)

As you can see from reading through the cases mentioned above, the law doesn’t require police to protect you or even to enforce the law. Combine this with precedent set by police unions and qualified immunity.