Dead fish? Buzzards? There's goes neighborhood

We had a stinky situation in our neighborhood. Literally. For the past week or more, the tilapia in our subdivision's lake have gone belly up and been floating on the surface dead. Not only did it create quite a stench, but it brought buzzards to our shores by the dozens. Ugh, what a scene. On a recent Sunday our homeowners association president and another neighbor walked the lake perimeter with rakes and big plastic bags to try to get rid of the dead fish. By the time the pair reached the back of our house, they said they had picked up 60. And they still had the other half of the lakeside to go. What was causing this dilemma? They weren't sure, but suspected someone had dumped something poisonous into the drink. If so, what a rotten thing to do. What the men weren't able to rake up and take away, the buzzards have tried to do their part, scarfing up the dead tilapia as they come to the surface and float to the shoreline. We love our wildlife, but what unwelcome guests.