Finn could only shake his head helplessly to answer Clare's question, a sign that he didn't know the answer to the question.
He then told the soldier that he lost consciousness shortly after being bitten by a zombie, and then was thrown away by the people who kidnapped him. When he regained consciousness, he realized that something was no longer the same with his body, and that was why he ran with all his might to get away from the bad guys.
He acted like a loser who ran away from the bad guys instead of trying to save his parents, and that was his biggest regret; he was even embarrassed to tell his friend about it. However, his friend patted his shoulder gently while saying that the tragedy was not his fault at all. It was already a miracle that he didn't lose consciousness after being bitten by a zombie, and that fact alone was something to be grateful for.
