Until a full report is published it is unhelpful to speculate. However, the above comments referring to possible over-torquing of the bolt are misunderstanding what a Thunderbolt is and how is works. As pointed out, the Thunderbolt design has a self tapping thread that is designed to work in brick and masonry, but it is of crude type and not equivalent to a self tapping thread used for metal or plastic. The article mentions the use of "resin": Thunderbolts are not intended for use with chemical anchors. One thing that is certain is that it is the wrong fixture and wrong application. The level of ignorance of whomever placed the bolts in this case is quite shocking.