Construction is a high risk occupation. There have been plenty of accidents at Watchtower that just aren't talked about. They take lots of safety initiatives, but it's not like there are guardian angels flying around the site.
Similarly, a crane tipped over at Patterson working on one of the residence buildings. The weights of the tilt-up panels are painted on them so the operator knows what he's dealing with. A panel was heavier than what was written on it. Crane operator lifted it and started to travel when "timber!", over it went. It was a Watchtower crane. They uprighted it, fixed the crane and the boom.