In all honesty Mikael felt really bad. Mark was the best friend who was dragged into this without an actual reason and he was being affected by everything just because he was a good friend. He had disappeared with Alex back then and no one was looking for him. Alex was too shocked by the incident so he couldn't blame him and Luke…he would be perfectly fine if he had disappeared for good.
It wasn't the same though for his best friend. He had been searching Mark for hours going through empty form rooms and basements. He even checked the huge fridges they had in the kitchen where they kept the meat and the vegetables. He almost froze to death while looking for him, pushing the dead animals from side to side so he could get a better view of the place but Mark was nowhere to be found.