With the AL outbreak, there was the talk of the early morning severe weather knocking out power and therefore leaving parts of the population vunerable to not getting enough warning in the late afternoon tornadoes.
Especially with that outbreak still fresh in everyone's minds, having this massive death toll yet again just seems unreal. I'm sure it will come out in the NWS Service Assessment as to "why" it happened here, but F4's and F5's going across downtowns have not been accompanied by this type of death toll since the tornado warning system really got established. 1966- Both Jackson MS and Topeka, Kansas had F5's through the cities, with the Topeka one pretty much through downtown-- 19 died in the Jackson area and 16 died in the Topeka tornado. 1970- Lubbock, TX had an F5 go through downtown, including having a skyscraper in its path. There were 28 deaths there. 1979- Wichita Falls, TX, had the massive F4 mow through the city-- 42 deaths.
Maybe here, there were special circumstances, like a large amount of fatalities in one building-- we'll see if a lot of the deaths happened in the hospital itself.