That does sound like some shockingly bad judgement on the troopers part.  I guess maybe they felt like they didn't have enough evidence to arrest him, but it's really lucky that this situation didn't turn out a lot worse.  As a medical provider in the bush I once treated a woman who had been choked to unconsciousness by her boyfriend.  She had petechia on her eyes and bruising on her neck - plenty of evidence - but she refused to press charges and ended up going back to him.  He strangled her to death a year or so later (then shot himself).  It's so sad to me when women who know perfectly well that they are living with their potential murderer can't break away from them.