This has been a tough week. Several of the names were personally familiar to me. I met young one woman briefly who is friends with several of my friends here. Two others were potential relatives of another friend who had been in contact with them and discussing family trees since their surname is not popular. It brings back remnants of memories on a very small scale of 9/11, when there was a flurry of email between friends trying to get in touch with missing people. I hope that as many as possible where not at home at the time and on residing or vacationing elsewhere.
As to why... these things happen and will continue to happen even though we try to minimize their occurence. It could be a sinkhole which Florida has been known to have. And as others mention, there were some indications that this building had real problems that were not believed to be as serious as they were. In time I'm sure we'll learn more after investigation. In the meanwhile, just a terrible human tragedy.