Pujiang Town, China A site with three tower crane collapsed back in 2009 that I had missed. The interpretation of the reporter is that the first crane collapsed "at the bottom" and fell into a second crane forming and "X". One person was killed and 8 were injured.
The accident occurred late in the day which may explain the limited death rate for two cranes collapsing on a working job site. Those injured were on the building and working inside on the floors structurally completed.
I was unable to find more pictures or stories to help put a bigger picture together.