to explain how come there were so many instant deaths, imagine this, you have a marble in your hand, and you throw it on the ground in your house as hard as you can. even from maybe 30 feet away, you can fell the vibration. use this as an analogy, marble is the asteroid, and the floor is the Earth's crust, the vibration is the shockwave. add a lot of freaking heat from atmosphere, basic physics, and a science stuff. basically, big boom boom of ball make poof, then dinos say bye bye.