I just want to note that Kelly and Lizzie are alone in Dunbar with Burts guns and ammo. And this has been said over the radio where other people can hear it.
Possibly a zombie soldier (that died in the prison) could try to get in, or more likely one of Scratches crew, who would now be more armed.
Whatever happens I believe this is an important situation.

Another thing is maybe the Behemoths and numbered ones aren't undead. Just wild mutations created by Ink. So the person inside is still alive, which Datu does not want to become.