Was the mamoth extinction due to a comet?

The discovery was made by scientists from the University of California at Santa Barbara...
The period in question is called the Younger Dryas, an interval of abrupt cooling that lasted for about 1,000 years ...
According to the scientists, the comet before fragmentation must have been about four kilometers across, and either exploded in the atmosphere or had fragments hit the Laurentide ice sheet in the northeastern North America.

Wildfires across the continent would have resulted from the fiery impact, killing off vegetation that was the food supply of many of larger mammals like the woolly mammoths, causing them to go extinct.

Since the Clovis people of North America hunted the mammoths as a major source of their food, they too would have been affected by the impact. Their culture eventually died out.