I think that it could be beast 11 because he killed the occtopus so that he could kill them himself instead of another monster killing them. Beast 11 dosn't seem as though he would help the kids and Joe because of what people say about him. They drank from a pond that might have been one of the groupes of "aliens" property. So that might of made the "aliens" want to kill them. They had help killing that occtopus.