"I don't really remember; all I recall was, while walking through the forest, I got hit in the back of the head and passed out," Jack lied. He very well knew what happened to them; he had killed them.
"Oh," Leo said, unable to discern whether Jack was telling the truth or not, given how innocent he looked. The thing was that Jack was actually unable to show full emotions on his face; his skin was dried because of being undead, making it difficult to display expression.
Internally, Jack was nervous. Revealing his secret would lead to an attack by every human in the shelter.
"That could only mean Mark could have killed them, but Mark couldn't have killed them that way," Leo said, knowing Mark wouldn't just kill his teammates like that. He knew Mark's ambition was to have the strongest team in the shelter. "But he's still a suspect until we find him."