The Doctor clung to Jack during those five minutes. Five minutes can, potentially, seem like an eternity when you're holding someone you've just killed. Panic had set in, the worry that maybe he could've saved Jack and now he wouldn't wake up. Then guilt over what had become of Jack, how much potential Jack had. Then grief, briefly. Had he the ability to wail, he would have. Instead, he allowed himself a few moments to cry.

After all, while Jack was dead, he was alone.

He had to snap himself together. Jack was not going to stay dead. Even limp in his arms, the Doctor could feel the wrongness of him. He felt time twist and snap back together, and Jack was alive again, breathing and asking questions the Doctor wanted to answer but couldn't.