For one California man, what happened on the screen was not the scariest part of the latest “Twilight” vampire movie.

Brandon Gephart was watching Breaking Dawn: Part One when he started “convulsing, snorting, trying to breathe,” his girlfriend, Kelly Bauman, told CBS13 in Sacramento.

Gephart is just one of several moviegoers around the country who have reported seizures during a particularly graphic birthing scene which includes flashes of red, black and white.

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A Salt Lake City man told ABC 4 that he began shaking and eventually passed out in the theater.

“I didn’t really remember what happened after that I think I blacked out,” the man said. “According to [my wife], I was shaking and mumbling different noises.”

“He started mumbling and he was blinking on and off with his eyes at that point,” his wife added. “I was kneeling in front of him slapping his face.”

Doctors say that strobing lights are known to trigger epileptic seizures.

“It’s like a light switch going off, because it hits your brain all at once,” Sutter Sacramento’s Dr. Michael G. Chez explained.

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Watch this video from CBS 13 Sacramento, broadcast Nov. 23, 2011.