We may have discovered the reason behind Kristen Stewart's serious look on the red carpet: She's worried the crush of fans and paparazzi could someday rise up and kill her!

The actress, who's been busy these days with 'Twilight'-related appearances, tells Britain's Hello! magazine that she struggles to "keep myself from crying sometimes" at events upon realizing how quickly things could get ugly.

"I don't feel very comfortable on the red carpet," she said. "I look out there at a thousand people and I realize they could rush me and assassinate me. No security could protect me. Ostensibly they're fans, but I think about them turning on me."