Green Advertising?

Even Green River in North Carolina isn't this green.  The photo above, courtesy of the National Post (Canada) is not retouched, at least not by me.  Apparently, someone threw something in the Goldstream River in Victoria, British Columbia, which turned it flourescent green for several hours.  No dead fish or animals were found, so the colorant was thankfully something benign. 

Now, just who would consider doing such a thing?  Some teenagers looking to pull a prank?  A mad chemist?  Or perhaps some larGE company that favors this lovely shade of green?  Just askin'...