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Here, you may submit your work for close scrutiny and edting. But I'm telling you right off: don't expect me to mince my words as much as I normally would. I have no intention to be cruel, but do not submit your work here unless you are fully capable of handling criticism.
Don't misinterpret-- in no way am I the final word when it comes to creative writing. I'm not going to take what you've written, shred it to ribbons, and rewrite it entirely with only one or two of the original sentences. In this post, I'd like to work together with the authors who submit their work towards improvement. That may mean going over the same piece several times, and there's risk of injury to your ego (a risk I shall try to minimalize...but a risk, nonetheless).
I'm only one person, and multiple sources should be consulted if you truly want to bring out the best in your work. But if you value my opinion, here's where I'll give it.

3nodding Alrighty. There are some things here that can be re-worded to make things run a bit smoother.
"Said a raspy voice" You can chop out the "Said" and turn the adjective into a verb. "Rasped a voice". The "Said" can detract from the adjective, in some cases. Since the sister is dying, you might want to choose a word other than rasped though. A raspy voice is defined as "grating". She's dying, so her voice is bound to be weaker. "a voice whispered hoarsely" might fit better there. Since you want to indicate that the voice came from below, you could piece the whole thing together as something like: "a voice whispered hoarsely from the ground". You don't need to use those exact words (your writing), but condensing the sentence like that can get the same point across with less of an awkward pause.
Kayla looked down, and found her sister lying there, drenched in glistening, scarlet blood.
Too many commas. The one between"down" and "and" can be removed. Or, you can turn this into two sentences. "
Kayla looked down in search of the speaker.
It was her sister lying there, drenched in glistening, scarlet blood.
This next bit may sound too picky, but in "scarlet blood", the "scarlet" is assumed as blood turns red when it is exposed to air. If you want to keep the scarlet bit in, you can ignore this criticism, or you can say that the sister was "drenched in glistening scarlet", or something like that. Then Kayla can spot the wound, and see with horror that her sister is drenched in her own blood.
Moving on...
When Kayla screams, remember-- she's in a large crowd. People are going to react. Some will want to call 911. Others may try to help Kayla when she starts to carry her sister away. This help she may accept or refuse. Never focus too much on your character that you forget their surroundings.
"Mika!" She cried. "Wha-What happened." Simple correction. Change the period after "cried" to a comma. And in general, the first word after a quote doesn't have to be capitalized. The quote and the "she cried" after it are still part of the same sentence.
Then her arm fell to the ground, and Mika lay there lifeless.
For effect, you might want to give this sentence a line of its own. The whole point of this sentence was to show that Mika had died. But the reader has more of a tendency to pass things over when they're in a whole paragraph. If you devote a whole line to one sentence, it gives it significance. You don't want to over use this of course, but it has its place in each story.
Now when she cries out and asks what happens, you may want to start some actual tears up then instead of her suddenly just sobbing.
she cried, eyes beginning to smart with tears
Something along those lines. Then when her sister is dead, she breaks into full sobs. And now that I think of it, you might want to have Kayla check and make sure she's actually dead. If your loved one died in front of your eyes, you probably wouldn't just decide they're dead without question. Even if you were sure, wishful thinking would make you check for a pulse, breath...anything to disprove what you already knew to be true.
Last sentence--the sobbing and the carrying can be two seperate sentences.

Despite the size of this critique, your writing really wasn't bad at all. ^_^ Start out with this, edit what you have...if you want to argue any point I made, go ahead. Repost the section after you've made your corrections, and we can see what room is left for improvement (that we can spot, anyways.)

You're welcome, and best of luck. 3nodding
^_^