Shelter dogs poisoned

[Catherine]

It could be someone who hates the shelter or it could be someone who was refused a dog for whatever reason. 
It could be a former volunteer or someone who was refused as a volunteer. It could be a former staff. It does seem likely that the person had a connection with the shelter. They must have had some knowledge of the building to find the dogs they wanted to kill. 

I agree, I hope this doesn't ruin the dogs chances of finding a home. They don't even know yet if any of the dogs are going to recover completely. It is going to depend on the nature of the poison and whether it has long term consequences.  They won't know until some time passes and the dogs stay healthy. The biggest fear would be kidney trouble or neurological damage.
It is a terrible thing to do to a helpless trusting dog in a cage at a shelter, a dog just hoping to find a home.