Just to stay real.... a closed car in the sun gets hot because of the windows.... a trunk wouldn't get as hot as fast.
I am sure it was uncomfortable, and would certainly be as hot as it is outside, and I don't know how well they could have gotten air in there, but the situation of a trunk is not like the situation in a closed glass greenhouse of a car.
Ok. I'm just in a goofy enough mood lately. I just ran my own experiment (admittedly, flawed.)Not trying to show anyone up or anything, but just out of curiosity.
No- I didn't lock myself in the trunk of a car ;>)
What I did do was take 2 thermometers, and place one in a trunk, and the other a shaded part of the same car's back seat.
The thermometers where not calibrated, and were not identical, but were the same type, and both had been in stored in the same inside area, and were reading 80 F before I placed their persective places.
Our outside temp was 88. I left them both in place for 20 minutes. The one in the trunk read 115. The one from the passenger area, 113.
Of course, this doesn't take into account the carbon dioxide factor, but 3 young boys in that sort of heat, in an enclosed area, would have succomb rather quickly...