In the transcript, at 19:11:54, the noun is "punks" not the racial slur on the altered audio tape.The genuine sound file is that of the government site, http://www.sanfordfl.gov/investigation/911/call1.wav and the phrase occurs at 2:18.
With headphones and a dozen replays the word becomes clear: "punks".
I heard PUNKS too, the first time I heard it.
The transcript was made from the file linked on the Sanford Police site. After several replays (no headphones), it was still unclear what was said — hence the [unintelligible] note in the transcript. I personally believe that it is more likely that he used punks or something similar and not coons but the sound is so distorted that he could just as easily be saying toast or jam.