I have noticed that people have many words available (especially because we all watch TV and movies) and they instinctively choose to use different ones in different contexts. Abducting two people isn't the same as asking them if they want pizza.
For example, it's interesting that on this forum we don't call Abby and Libby 'guys', but we do use the word to describe the perp.
A police officer who is about to arrest you and your accomplice won't say "Guys, put your hands up." Someone might say to police "Guys, I'm innocent", but smarter ones will say "Officers".
As the detective said, this crime was about power. The word 'guys' is used in an everyday context, because it avoids expressing power. When you want to express your power, or acknowledge someone else's, you don't normally use that word.