My first reaction was that this was another Mossad hit on Hezbollah, that may still be the case, but the fact that Israel is coming out and demanding UNIFIL to investigate this makes it look more like a Hezbollah blunder rather than anything covert.
then that’s one monumental blunder - it’s one thing if a weapons depot goes KABOOM with a couple underlings in the building, it’s a whole other level of screw up if there is a head honcho present