Alucard already knows how being hungry as a vampire feels, considering that he's been one himself for hundreds of years. The unquenchable, maddening thirst for blood that he's felt when he's been too much time without feeding is something that's not easily forgettable, even if he's learned how to manage it. So he already expected this to happen at some point. Young vampires tend to have trouble controlling themselves at first, so it's nothing new to see his kid acting like this with how little time has passed since he turned them. But he's still worried. This is his own child, after all.

"Stop. That's enough." He says, his voice stern but not completely harsh. He wasn't against his kid attacking intruders, it was a nice and easy way of keeping the manor clean. But he didn't like seeing a literal child acting so violently, looking so sadistic. Maybe his own habits are rubbing off on them, and while he feels just a tiny bit proud, he understands that this shouldn't be like that. It's his fault this child became a monster.

"That man is dead already. You don't have to keep attacking."

He reaches one hand out, grabbing the kid by the shoulder, carefully but firmly tugging them away from the dead body. He doesn't want them to be drinking that blood, either. It's probably of bad quality.