The addresses on those mailers will identify the EXACT route and EXACTLY who the mail carrier was that threw those fliers in the dumpster.
Routes, and any part of a route, are assigned to specific carriers.
Postal Inspectors should already be investigating this crime.
Years ago I went into an electrical meter room for a very large apt complex to do some phone work
The floor had about a foot of bulk/junk mail on it.
It was loaded.
Carrier was throwing it in there vs delivering it to the individual boxes
I called the PO
Found out later carrier was canned
Yup.