I drove up thinking it was a Refer unit having a hard time starting with the black smoke. (again not bad yet). As I start to go by I noticed Fire/plastic melting off the bottom of the unit. Went up to the Pacific Pride (100 yards away or so) go back to the parking lot and about 5 people standing there confused. I yelled out lets get it disconnected and that”s when they went into the next step in sloth mode. Driver was no where around, so I was going to disconnect it myself or help disconnect his truck if he showed up. Got the landing gear cranked down and was waiting for another driver to bring his fifth wheel release handle because melting plastic was dripping so I could not get it by hand. By the time the driver brought it to me it just took off quickly so we all backed away and watch it burn until the Pasco Fire Department, Pasco Police arrived.