Welcome to BYC, though I am sorry it is under sad circumstances.
I am so sorry for your loss -- the fact of the matter is, though, that losses do come with this hobby -- even when you do everything "by the book" sometimes chicks die. I did notice you said the temperature is 95-100, that is rather warm. Even in the first week you really only need 90-95 (many of us don't even measure temperature, choosing to use the behavior of the chicks to judge what is too hot, too cold or just right), at the warmest place within the brooder, and the rest of the brooder should be cooler to allow the birds to be able to self-regulate their temperature by moving into and out of the "warm spot"....the temperature should reduce as the chicks age and feather in as keeping it very high when they have more feathers leads to overheating. Over-heating can lead to death - though there is no way to say for certain that is what caused this chick to pass. How long have you had these chicks? Can you post a photo or two so we can age them by the amount of feathering -- or tell us if they have a few wing feathers, fully feathered wings, some feathers on their chest, etc....those are stages of feathering that allow us to judge their age. What are you feeding our chicks? Is fresh, clean water available at all times? Is the bedding perhaps pine shavings? Are the droppings you see in the brooder normal chicken poop or is it runny,funny colored, smelly, etc? You say the box is "big enough" - how big is it (feet long by feet wide)? Are you using a lamp or alternative heat source?
I know this seems like a lot of questions - it goes back to there being many potential causes of loss when raising chicks and answering some of these questions helps us take things on/off the list until we are able to maybe narrow down what happened to this chick. In the end, it may just be that this chick was failing to thrive and finally got down enough that there was just no coming back. The trampling you saw is often the first indicator new folks have of something going wrong and, by that point, it is often already too late.