Rim Removal

I recently pulled over to help a motorist fix a flat and I was unable to help them. It looked like an older Corsica (90-92). The back tire appeared to have a center lock holding the tire on the back axle. Is this true? If so what tool does it take to remove it and which direction does it have to be turned? Their car is still on the side of road and I thought it would be nice to replace their tire before tomorrow morning anonymously after I saw a childseat in the back.

Probably too late for this but I have not seen this myself. Perhaps a newer model though.... Mine has a center cap that simply snaps out. Most I have seen do that.