What are John and Mary talking about?

M：What are you doing, Mary?
W: I am cooking the dinner, John.
M: Oh. Look! The Capital Building caught on a big fire today.
W: What? How about the people in the building?
M: More than 220 people were killed and the building was destroyed.
W: It must have taken the fire fighters a long time to put it out.
M: Yes, they spent about five hours putting it out. Hm, what a strange smell!
W: Oh, I forgot the food cooking on the fire!
M: Be quick! Turn the gas off. You should be careful next time, otherwise you’d have our house on fire!