The most he could muster was a shrug and an "I know." He couldn't say it was okay, or that it wasn't his fault. Cole hated what Sam had done, but he didn't hate him, and he definitely didn't want him dead.
Time. He just needed time - to cope and move on, and to give Sam a chance to prove he had learned his lesson. Now that he knew the consequences of his actions, he couldn't ever do it again.
"I think... I'm going to head up. I need to sleep," he said, once they'd gotten back to the building. "But I... just let me know you're okay in the morning." Let me know you haven't killed yourself overnight. As much as he wanted to make sure Sam was okay, he needed to be alone.