The vets don't know, and the poison control couldn't figure it out. They treated both dogs with meds for the highest neurotoxin they had knowledge of and that couldnt save Sam. The last time I had a complaint about the dog was when I only had Chloe and she was about 9-10 months and she's 25 months now and no new complaints since then. But I still believe it couldve been either the next door neighbor or a neighbor a few houses down!