Some plot holes I couldn't figure out (spoilers)

[The Real Ish]

I can't figure out the motivation the whistling man had to kill Jimmy and also why they spared Carrie.

And who is the person in the intro scene who is ambushed (maybe killed) by the whistling man? Clive?

[Agent Janek]

Yeah it´s a theory that first one was Clive

Also if you paid attention to story, you could see that Carrie was a victim of prank of her stupid friends & due to killer motivation of prank too she saw her as a innocent victim and let her live, perhaps it reminded her of her situation back then

[Sgt Reed]

Jimmy played the same prank that killed her man and Carrie was the victim of it.