How would humans react?
Us humans and animals would react very frightened, trying to gather precious things in time so they can save their family. Humans would try their best to save them and their families and leaving the animals. Animals have lives like us they would be extremely scared as well.
How can they start?
Bushfires can start in any way usually the cause of fuel which can create an extreme fire if it is close up with flames. Wind can cause fires if there is a high temperature it could also happen this way on a slope angle.
National Gepgraphic Geomorphic Hazards | Page 9