Hello; Noticed that the tank was near two windows. Not sure where Killeen is but if you are in the area where there has been very high temperatures, perhaps this had something to do with it? I know that when my area had several 100+ degree days that surfaces would get very warm to the touch. This would be more so near a window. Maybe a big enough thermal change if the AC was turned a few degrees cooler or just kicked on with the return of you and the family? Even so there may have been some sort of flaw in the glass.
Any way , sorry to hear of the troubles.