I’m interested in how they got their suspects narrowed down that drastically in the first place.

They listened in on the chat he was in and could glean from chatter that he lived in a particular municipality or something, rough area. Stuff like, dunno, complain that the supermarket is closed because they had a water leak or something and pin-pointing that. The rest was driving around and see if anything correlates roughly, then park there long enough to make that correlation court-proof.