02/28/2012 03:53 am ET Updated Apr 28, 2012

Ed Helms Talks Blacking Out Trying To Help An Injured Friend On 'Late Show' (VIDEO)

Ed Helms thought he was going to be akin to Superman when faced with a crisis situation. But when faced with a real emergency, he proved to be quite the opposite, according to the story he told David Letterman on "Late Show" (Weeknights, 11:35 p.m. EST on CBS). The scene of Helms' would-be heroics was on a boat out with his buddy.

They were surfing, and things were going just fine until his friend wipes out and then comes to the surface screaming that he'd been hurt. The board had broken and in the crash had apparently sliced open a pretty impressively sized flap of skin at the guy's knee.

"I go into bada** mode," Helms said, but it wouldn't last. He rejected an offer from their captain to sew it up, because this was his time to shine. But something else happened as he was sitting there with the first aid kit staring at his friend's open knee.

"I'm cleaning it and then I start to go into shock," Helms admitted. "And I start to get nauseous and tunnel vision. I was about to vomit into the wound.

The story doesn't get better from there. "So I black out and I came to about an hour later," he said. It turned out he wasn't the hero his friend needed in that moment. It was up to others to step up and help, and probably help Helms as well until he came to.

Ed Helms stars in "The Office," airing Thursdays at 9 p.m. EST on NBC. "Late Show" is on weeknights at 11:35 p.m. EST on CBS.

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