Are the police legally obligated to protect us.

THE POLICE AREN'T LEGALLY OBLIGATED TO PROTECT YOU
Without even thinking about it, we take it as a given that the police must protect each of us. That's their whole reason for existence, right?
While this might be true in a few jurisdictions in the US and Canada, it is actually the exception, not the rule. In general, court decisions and state laws have held that cops don't have to do a thing to help you when you're in danger.
In the only book devoted exclusively to the subject, Dial 911 and Die, attorney Richard W. Stevens writes:
It was the most shocking thing I learned in law school. I was studying Torts in my first year at the University of San Diego School of Law, when I came upon the case of Hartzler v. City of San Jose. In that case I discovered the secret truth: the government owes no duty to protect individual citizens from criminal attack. Not only did the California courts hold to that rule, the California legislature had enacted a statute to make sure the courts couldn't change the rule.
But this doesn't apply to just the wild, upside down world of Kalifornia. Stevens cites laws an cases for every state — plus Washington DC, Puerto Rico, the Virgin Islands, and Canada - which reveal the same thing. If the police fail to protect you, even through sheer incompetence and negligence, don't expect that you or your next of kin will be able to sue.
Even in the nation's heartland, in bucolic Iowa, you can't depend on 911. In 1987, two men broke into a family's home, tied up the parents, slit the mother's throat, raped the 16-year-old daughter, and drove off with the 12-year old daughter (whom they later murdered). The emergency dispatcher couldn't be bothered with immediately sending police to chase the kidnappers/murders/rapists while the abducted little girl was still alive. First he had to take calls about a parking violation downtown and a complaint about harassing phone calls. When he got around to the kidnapping, he didn't issue an all-points bulletin but instead told just one officer to come back to the police station, not even mentioning that it was an emergency. Even more blazing negligence ensued, but suffice it to say that when the remnants of the family sued the city and the police, their case was summarily dismissed before going to trial. The state appeals court upheld the decision, claiming that the authorities have no duty to protect individuals.
Similarly, people in various states have been unable to successfully sue over the following situations:
when 911 systems have been shut down for maintenance when a known stalker kills someone
when the police pull over but don't arrest a drunk driver who runs over someone later that night
when a cop known to be violently unstable shoots a driver he pulled over for an inadequate muffler
when authorities know in advance of a plan to commit murder but do nothing to stop it when parole boards free violent psychotics, including child rapist-murderers
when felons escape from prison and kill someone
when houses burn down because the fire department didn't respond promptly
when children are beaten to death in foster homes
A minority of states do offer a tiny bit of hope. In eighteen states, citizens have successfully sued over failure to protect, but even here the grounds have been very narrow. Usually, the police and the victim must have had a prior "special relationship" (for example, the authorities must have promised protection to this specific individual in the past). And, not surprisingly, many of these states have issued contradictory court rulings, or a conflict exists between state law and the rulings of the courts.
Don't look to Constitution for help. "In its landmark decision of DeShaney v. Winnebago County Department of Social Services," Stevens writes, "the US Supreme Court declared that the Constitution does not impose a duty on the state and local governments to protect the citizens from criminal harm."
All in all, as Stevens says, you'd be much better off owning a gun and learning how to use it. Even in those cases where you could successfully sue, this victory comes only after years (sometimes more than a decade) of wrestling with the justice system and only after you've been gravely injured or your loved one has been snuffed.