Longtime climber and conservationist Mark Hesse died while climbing at the Boulder Rock Club this past January, but until this week it was unclear what actually caused his death.  While it is still not entirely clear what happened since nobody witnessed the accident, this article in the Boulder Camera seems to indicate this may have been another instance where a climber thought they were clipped into an auto belay system when in fact they were not:

The climber who was found in January after falling at the Boulder Rock Club died from blunt trauma, not a medical problem, officials said, and the popular climbing gym has since started using a new belay device to improve safety.

If that is what happened, this is the 2nd such incident to happen in the past 6 months.