One thing they never mention about the shadow bind jutsu is that you can feel when the target dies. The shadow bind, after all, can be fought by the user's own chakra. So even untrained civilian targets or the unconscious and unresisting create a slight pull felt by the Nara holding the jutsu.
When they die, a caster can feel a sudden slack in the line, a release of pressure signifying that there is no longer any chakra to resist the jutsu.
So while Nara Shikaku did not slit any of the kids' throats himself, he felt their deaths far more intimately than the ANBU operative who did.
The kids had had to die because their father was a bandit on the edges of Fire Country. The local daimyo wanted him and his woman dead and the entire (thankfully small) clan wiped out, their house burned to the ground, as an example of what happened to those disobeying the laws. It was not a hard mission logistically, but the family included half a dozen children, which was an automatic flag for an ANBU assignment. Even jounin could get messed up by that sort of shit. ANBU were usually already messed up, so what difference did a little more make?
Shikaku had gotten tagged for the mission (he'd been back in ANBU a WEEK. The fuckers.) because his shadow bind was perfect for grabbing multiple targets and holding them. And with untrained, weak targets like children, he could have held them there indefinitely. And he did. He held the children still, as though he had turned them all to stone, while a teammate fought and killed their father, and then their mother. After all, the parents were the only real threats there.
He had closed his eyes, to make the children close theirs. He couldn't stop them from hearing, though. And when their parents were finished, he opened his eyes to see the children, turned white with fear and still immobilized. They looked like carvings, already dead. But they weren't dead, and he felt more than saw each and every one of them drop to the quick ministrations of a kunai. Heap the bodies in a makeshift pyre in the house, use a fire jutsu to start the blaze. Mission accomplished.
That night, he went and got drunk at a local bar. Then he snuck into his house, avoiding his and his wife's room to head into his son's bedroom. He fell asleep there, watching Shikamaru sleep.
A/N: These are the drabbles I've been writing for the RP ScarletSpiral, where I play Nara Shikaku. The RP is set nine years before the start of the series and focuses on the members of ANBU. This was written for my application, where I was required to write about Shikaku's reaction to being assigned to kill a child.