Garibay told NBC Chicago that staff quickly had his group shuffle away from the nightmare box, but that "They jokingly and confidently responded, 'It's unbreakable'", so the tourists snapped a few photos and moved on.
A spokesman for Willis Tower said Thursday it wasn't actually the glass that cracked, but rather a protective coating covering the glass.
"Occasionally this happens, but that’s because we designed it this way", Bill Utter told the Chicago Sun-Times. “Whatever happened last night is a result of the protective coating doing what it’s designed to.”
Apparently engineers are now developing protective coatings to scare the piss out of everyone.
The Ledge opened in 2009, and constitutes four glass cases composed of 1.5in-thick glass that protrude 4.3 feet beyond the building.