WHO KILLED THE CRAWFORDSBURN RIVER ?

On the morning Tuesday 12 October 2010, a local angler reported large numbers of dead fish in the Crawfordsburn River from above the viaduct down to the shore.
The river was brown in colour with foam in places.
He reported this to the Country Park Warden, who contacted the appropriate authorities.
They investigated this and traced pollution in the river above Crawfordsburn village as the river heads towards the Craigantlet hills.
At least 200 dead fish were seen in the river with many more being washed to sea when the river was flowing brown. The stock of wild fish in the river has been destroyed along with other insect life.
WHY DID THE FISH DIE ?
WHAT KILLED THEM ?
WHO KILLED THEM ?