Leopard Gecko and cold

Question
My son lost his heat for a day and his house was 35-40 degrees Fahrenheit for approximately 5-6 hours. When we got to his Gecko, I brought him out to the warm car, I checked on him and he was almost dead. I held him and put him up near the heaters, he finally began to move, but he was twitching and almost convulsing for a bit. I left him in the car (on the front seat) with the heat running which probably brought the inside of the car and his aquarium up to 80-90 degrees Fahrenheit, but when he walked he was still twitching. When we got him home, he was dead. I just want to know if I killed him because he got to hot, or he warmed up to fast, or was it because he was so cold. I feel terrible and I don't know how to tell my son that he is dead, I just wanted to know what I may have done wrong. Thank you.

Answer
Hi Michelle,
I am sooo sorry your leo died. I'm guessing your son lost his electricity because geckos do have to have heat sources from top and bottom..IE:  heat light above and under tank heater.
It is always a good idea to have heat packs for emergencies.  You can purchase ones that can provide heat for a few hours to 40 hours.  The ones that people use for feet, hands, etc are fine.
Now, on to your gecko. Think of a person that has hypothermia... regardless of how slowly the proper temperatures are brought back up, there is either life long complications or death because the organs just can't recuperate from the too cold of temperature.
It really is hard to know for sure if he was re heated too quickly but given the temperatures he was subjected to..it could have gone either way with him.
Personally, I would go with "he just got too cold" as the reason.
For future reference, in addition to the heat packs... the best way to re warm a too cold reptile is starting with lukewarm water and going slowly from there...but..as I said, sometimes no matter how slow you re warm them...it just may not work to save them.
Again, so sorry for your 9and your son's) loss.