It was March, 2004 when my Grandpa had his first asthma attack
I was only in the third grade then
^So if this was 5 years ago, and you were in the third grade, then it would be logical to deduce that you are in the 8th grade now. Is this really the case? If so, it is a bit early to consider College admission essays.
Tears were running down everyone's eyes but not a sound was heard except for the uncontrollable cacophony of weeping.
^Cacophony implies that it was a lot of heavy and unpleasant sounds. It is the incorrect word to use in this sentence, given the context and the dramatic effect that you are attempting to create.
Your essay is very unclear. There is a spoiler in your essay, in your first few sentences.
Furthermore, you do not recreate the scenes vividly, so this does not suggest why this was a significant experience and what makes it significant to you.
Your grammar needs considerable revision. You use semicolons unnecessarily.
Your essay is quite weak as it stands. The writing style and grammar fail to support the content and your point of view, which in effect, makes this an ineffective essay.