That's what happens when someone with insufficient brainpower tries to make logical connections. It almost makes sense if one was raised on Ebonics: How many guns? Dozens of guns. Ooh, how many dozens of guns? Two dozens of guns... Maybe the reporter had it right and the editor was a "diversity" placement.
My point wasn’t the misuse of the language, but the hype, as if the two dozen figure was some incredible amount.