The female deputy that narrates the majority of this episode is absolutely horrible- living in Iowa I certainly hope I'm never left to her devices as an officer.
I've said many times the nonsensical byline standard of cops that 'oh they didn't have a normal reaction!' is obtuse- 1) she was lying next to her fiancé and drug into questioning, MAYBE SHE IS IN SHOCK?!?! Maybe she's very even and unemotional, you don't KNOW HER, you can't possibly know what her baseline is. 2) you are not a psychologist so leave this type of thing to professionals who will tell you 100% how wrong you are.
This is precisely why, no matter how innocent you are, you should absolutely, positively ask for an attorney before any questioning occurs. There's far too many innocent people who've served significant time/been executed to ever take a chance that 'if you have nothing to hide you don't need an attorney!', cops say this because it makes their job harder and requires them to follow the letter of the law. A skilled attorney will instruct you what they can/cannot ask and what everything means; left alone with this abhorrent mess and you'll wish you hired one.
It's cops like this one that prove how easily you can find yourself a lead suspect and trying to repair your life when you've done nothing wrong; this poor girl was as much a victim as his mother, having witnessed her fiancé shot at point blank range, and all because a psychopath she dated a handful of times was unreasonably filled with rage through no fault of her own.
This reprehensible excuse for an officer should be forced to issue a written and very public apology for her statements.