Air sirens had already started so most people had moved down to the basements. Probably some people who couldn't, or who were caring for those that couldn't be moved were caught in the blast.
Brutal thing to do. At least they didn't go for a double-tap, just for the lulz.
This is tragedy. I find it so weird, though, - rocket hits hospital (!) and only 2 dead, both adults, and 16 injured.