How does the inside gl of a double pane sliding gl door shatter, if nothing caused it by impact?

We heard a loud pop and it started to crackle. There is a starting point but nothing had hit it and it happened the the inside of the house panel not the outside. 'I do it was cold earlier and we were cooking so it was a little warm inside but the panel is prob 5yrs old or so. How did this happened? Im so confused. Please respond only if you are a professional or recieved your info from a professional. Thanks