Ongoing controversy in comet blast 13,000 years ago over N America

I find it difficult to understand how something could kill all the megafauna. Something dramatic would have to happen.

What survived were frogs, salamanders, crocodiles, and animals that could hide in the water or underground. Most of the large animals vanished.

Perhaps the blast caused widespread fires. Perhaps there was disease.

http://www.newscientist.com/article/dn18175-was-there-a-stone-age-apocalypse-or-not.html

Also, perhaps the animals were spooked by the fires and ran until they were exhausted? This is what is done in persistence hunting.

http://en.wikipedia.org/wiki/Persistence_hunting

Something must have happened to cause the death so many large animals in North America. It seems difficult to believe that they could all have simply been hunted to extinction because I think the human population was too small... but maybe not.

http://en.wikipedia.org/wiki/Quaternary_extinction_event#North_America