Off Duty Trooper appears to be first on scene
Not sure of how CSP does their off duty call signs,....
On Broadcastify, the Denver CSP Dispatch archive for 15 November, start time of 20:38 - run it up to about 11 minutes on the counter and you can hear him calling this in.
Douglas County dispatch informs Castle Rock Fire that there is an off duty Deputy reporting this to be a DOA as they are dispatched, time around 20:53