So you saw someone commit a federal crime, at least I think intentionally killing migrating waterfowl is still a federal crime.
They were in a $400,000 boat, how many can there be on the lake? You should report them.
We're not talking about someone chasing a seagull in kayak.
Call the MP and the US Fish and Wildlife Service. It's a federal crime, the FWS has jurisdiction.
http://www.fws.gov/migratorybirds/Re.../mbtintro.html