There's one good thing about living in a county (Park) the size of Rhode Island that's covered by one deputy on the night shift; they more or less expect the bad guy to be assuming room temperature by the time they get there.
When I dispatched in a town of 40,000 in the Midwest, response time was well within 5 min or less on something of this nature, again, unless you lived way out in the county. I imagine Big City response time is about the same as county time. Remember, the Supreme Court says they are not there to protect YOU, only to protect SOCIETY.
Probably 95% of the cops we had were damn good, very professional, but think of what a nightmare it is for THEM to be entering a darkened house not knowing how many people there are, BGs vs. innocent civilians, who's armed and who isn't. Even with the very best response times, I'd advise dealing with the problem yourself with Glaser safety slugs in a pistol or a shotgun with birdshot to avoid over-penetration, especially in modern houses. Meet the boys in blue at the door under the porchlight with your hands empty and tell 'em what happened.