Try "wow, how insane!"
Try applying Occam's razor. What happened 13,000 years ago? The current "native-americans" who came from Mongolia arrived, and quickly hunted all the big game to extinction.
The same extinctions happened, at a different time, in Madagascar, when Asians arrived. So are we to believe, i.e., that two DIFFERENT supernovas can explain that extinction cycle?
Rubbish!!
My theory is that our ancestors combined the atlatl (100 yard range and good penetration but poor accuracy) with Clovis points (grooves hold the poison) and a simple poison like nicotine or aconite (from Monkshood flowers). Large herd critters like mammoth would be easily dispatched from a safe range and the tribe would feast for a week. Smaller, harder-to-hunt critters like elk and deer were spared.