of course there needs to be an investigation... but unless its clear that the person is a flight risk, i would've guessed that the investigation can be done without treating the "crime victim, protecting his home and family" like a criminal himself.
If i was protecting my family and my property, and the SOB, willfully and deliberately intruding on my property, got off'ed in the process, and i would be arrested, as the cops do, chucked in jail with other criminals, who unfortunately did not get shot up, and the investigation proves that i was just acting on my rights to protect my own, then i'd be very much inclined to sue the cr#p out of all police ministry and government.
As has happened before, where the police dept. had to cough up quite the fortune.
So, one would think it in everybody's best interest to investigate first, then arrest?
otherwise one might get to the impression that, if somebody intrudes on your property at night, the best advice is to take all steps to snuff the bastard, and chuck his body out on the street. "i didnt see nothin"

who needs the agrevation from the justice system when they couldnt protect your property!
of course... thats not the way to go, but.....