An asteroid heading towards the Earth

Just thinking. Suppose an asteroid were discovered heading towards the earth and it is calculated it will hit the earth and wipe out all complex life, including humans. And suppose the impact were to occur in 9 months time. I imagine people would panic. No one would go to work. Civilisation would break down. Power would go. All the supermarkets would be quickly emptied. So, in fact, most people would die in somewhat less than 9 months?