Just so you know... creepypasta is fiction and they've even had to come out and say so multiple times. So whatever recording you listened to is probably also fiction...
The recording is legitimate. Here it is on archive.org, where I listened to it: https://archive.org/details/ptc1978-11-18.flac16
Following references on Wikipedia (which would have been a better way for me to find a reference in the first place), here's a site on SDSU with the tape and several transcripts, one by the FBI: