Good post, and I agree with the assessment.
"Guys" is used all over the place, but I think it's more common along the northern tier of the U.S. vs. the Old South, in between is a mix, including Indiana. I hear both it and "y'all" around Fort Wayne. I've heard it from folks on both coasts, too. The mountain states. Etc.
I'm detecting what's called a "Northern Cities Vowel Shift", or "Inland North American English", type dialect just off of that one word he said. Also sounds like there is a lilt or distinctive pitch change, from low to high, when he says it. He's getting their attention, plus he might be nervous/anxious some as he puts the wheels in motion for his crimes. It's clipped, kinda short when he says it. Sounds to me like "guise?", or "guize?".
JMO
-FD