someone rear-end hit and ran me and i don’t know if i should add another vehicle to the crash report

Last night i was driving home after getting food and got completely rear-ended at a red light, with no effort to stop. The car immediately fled before I could get a license plate number or the make. Paramedics showed up but the PD never did, and i’m now filing a crash report on the colorado dmv website as instructed. I’ve already filled out my information, but i’m not sure if i should add another vehicle and out “UNKNOWN” for certain parts. This might be a dumb question but I don’t want to mess up here, any help is appreciated.