They showed a car on the news, a mid-90's model Toyota Camry sedan. Those cars have fold-down seats in the back row that open into the trunk. Unless it was just a shot of a random car, I don't see how they could have trapped themselves in the trunk.
I wondered how the kids got into the trunk...the fold down rear seats could explain that. (Entered the trunk via the passenger compartment) Don't those kind of seats fold forward--into the passenger compartment? If that's the case, then it means the last kid into the trunk had to pull the seat up?