<a href="https:&#x2F;&#x2F;youtu.be&#x2F;vuet3t9geXo?t=11m59s" rel="nofollow">https:&#x2F;&#x2F;youtu.be&#x2F;vuet3t9geXo?t=11m59s</a><p>Start with this.<p>The size of the asteroid they thought would be the size of Staten Island, NY. The impact would generate a huge shock wave and high temapture, fire everywhere, so killing animals nearby (say 100 miles) within minutes.<p>Tsunami came next and wiped out everything nearby hundreds of miles+. The smoke and dust covering the air (think of volcano) so sunlight cannot enter Earth so there was a long cold winter, killing even more animals.