Ecto 1: Hearse or ambulance?

Can someone tell me what ecto was before the Ghostbusters got it? It looks like a hears because its black and had those curtains. But it also had a siren and lights. Was it used for both? Ive read about it on here and it seems that model was a limo/hearse/ambulance. Just kinda wondering about any backstory that might go to it either in the gb universe or reality. What was ecto used for?

It was a multi-purpose vehicle. Rollers on the floor in the back for caskets or stretchers, with flip-up jumpseats for early paramedics. This was very common for professional cars made before the mid-70s.

Oh ok thanks guys. I read the reference page like a year ago and I must have missed that part about it being used as both. Sorry to post threads about info thats readily available. ill try to do more research so i dont wast any ones time. Lol but thanks again guys.