Hartz Flea drops almost killed my 2 cats

I put Hartz flea drops on my 2 cats on 2-21-03, the next day at 2pm my cat Bingo started having convolusions. I was trying to hold him and talk to him while he was having it. Once it stoped after 20 minutes he was still shaking and having body tremors. I rushed him to the vets after they talked to me they asked me if he was on any meds. I told them I had used Hartz flea drops on him last night. The gave him so shots to try to stop the shaking and then washed he really well he was still have body tremors. They kept him. Then I come home an hour later my other cat was sitting on my bed shaking really bad so I rushed her to the vet. They both had to stay 24 hours and they are now home and on muscle relaxers the one cat is still having lots of body tremors. They both can’t seem to keep their blance. The vet is not sure if the one cat is going to make it and she thinks they will both have permanent damage. Its so sad, I feel awful I would have never used this stuff on my cats if I would have known It could kill them and it has already killed many. It should be taken off the market.