Why did jack leave in chapter one of the graveyard book?

He'll have to make contact with certain townspeople who will tell him if the boy turns up. There's still plenty of time, many years, for Jack to complete his mission and kill the baby. When he hears the police sirens coming to the house where he did his dark work, he walks off, his big knife in his pocket.

Explanation:

because, you have to i : /

hope this ! =)

cutie~

c he talks about the us lives lost.