My Cousins Cat

My cousin had a gorgeous black tiger cat. They had used Hartz flea control on him because another house-cat of theirs goes outside. They put the flea medicine on him while he was laying down. He sleeps a lot as normal and about two hours later they went to feed him. He wasn’t moving when they got the food out. My cousin went to pet him and he was completely cold. He had died within the two hours they put the flea medicine on him. He was a healthy cat, no health issues. We all strongly believe it was the Hartz medicine.