You're talking to someone who followed these events from the start, and happen to live in the country where they happened. At least one of them did BOOM themselves in the auditorium and ALL of them were wearing suicide vests. Also, the one who blew himself up entered the auditorium, which was, at the time, full of students because an event was taking place. He forced the students to gather around him, and he blew himself up. There's not really any excuse or reason to attack schools in any kind of conflict. And did I mention the other explosives they planted in the school?
And many of these militants do suffer horrible deaths. They get picked up by agencies, and tortured to death. However, it's not legal. Punishment should be public and should set an example. It should not encourage others to do the same deeds.
Oh, and there's also significant evidence of Afghan Involvement.