My little Oreo died

I bought Hartz Control Pet Care System Spray For Cats. My little Oreo was 3months old. He was such an energic cat, no wonder the pet shop gave him the nickname Jet Li went we bought him. Oreo had fleas so i tought that product was okay, how coudl i know ! So… maybe a week later he started vomiting, diarrhea with blood, he did not want to play, he was miaowing for nothing, and it kept going worse … At the end he wasnt movign at all, he was deshyatred, he wasnt eating, his eyes werent moving, he was dying under my eyes. I went to the veterinarian, and it was too late, he was near hid death. Even the veterinarian didnt know what he had, theres was nothing really wrong. We tought it was a virus that killed him. He was just 3 months old, i had to put to sleep my precious baby. A week or 2 after, i wanted to know what really hapenned , i looked on the internet for all the possibilites. Then i realized it all started after i bought the Hartz Flea Gard. I feel so guilty now that i know that i killed him. I don’t understand why they still sell this product…poor naive people who think they do the right thing for their love one…. if i knew

RIP my baby Oreo i luv you so much and i miss you