a heater? what kind of rag tag zoo is this?
People who deal with animals sometimes use electric heaters. I don’t know the facts, but the suggestion that it was a heater may mean that they inadvertently used a defective one.
(On the other hand, I’ve seen idiots walk into horse barns smoking cigarettes.)
One that is trying to keep tropical animals warm when the temperature drops below freezing, as it did last night in Virginia.