I find your line of questions repugnant, in the sense that it would seem you're examining it from every angle possible to find one tiny weakness that could help you dismantle the simple fact that they bombed a school full of children.
1) I dont think all the involved military leaders are such cartoon villians that they would intentionally strike a school full of kids
2) I especially dont think they would do so with the intent of a follow up strike exclusively for killing the first responders to the atrocity from (1)
Delivering two bombs to a military target doesn't seem unreasonable. The fact that two missiles struck the school is not evidence of (1) OR (2). If there were significant intentional delay, that would change my assessment. There doesn't seem to be, in this case.
What the hell do you think he meant by that? Because this is the exact thing he meant by that.
Note that this kind of "Double tapping" was commonly done in strategic bombing in WW2! It's done because it's a very effective thing to do! Or at least, it usually is if you have an actual plan and strategy.