Statements that the Ukrainian military suffered no casualties in today's attack on Sumy, is true.
They were in a bomb shelter with, among others, children who were at a dance festival in the same building.
It could have been absolute carnage because I hear there were almost 100 children in the same building, with parents and grandparents. Everyone went into a bomb shelter and escaped without injury.

So, what we have as of now regarding the Sumy attacks:

Ukrainian MP Maryana Bezugla essentially admitted that an awards ceremony was taking place there at the time of the strikes.

A geolocated image showing the Ukrainian triangle tactical sign on a pick-up truck (the kind which is regularly crowd-funded) which operates in the Kursk direction (Sumy is right next to Kursk) was seen next to the impact site.

The mayor of Konotop (a city in Sumy Oblast) said in a livestream that the awarding of certificates and medals for the 117th territorial defence brigade was taking place there.

And there is also the fact that the 117th territorial defence brigade was formed on April 13 (exactly 6 years ago). Therefore, it would be natural to hold an awards ceremony on that specific day.

This war is so stupid. Those in the UK and US who pulled Ukraine away from the Istanbul negotiations should pay a heavy price for this.