Police say a fire broke out at Happy Cat Sanctuary on Dourland Road in Medford Monday morning.
The owner Christopher Arsenault was killed.
The group estimates 100 cats died and tells News 12 between 150 to 200 cats survived.
There is an effort to help the surviving cats.
A GoFundMe page was started and already has raised more than $130,000 to pay for vet bills.
Many cats have been rescued, but volunteers with Strong Island Animal Rescue League believe there are still more that need to be found.