(PHILADELPHIA.CBSLOCAL) — It’s a mysterious brain illness that triggers psychotic and violent behavior. It is rare, and it is often misdiagnosed. One desperate family grabbed a video camera to document what was happening.

In the tape, seven-year-old Paul Michael Nelson can be seen yelling uncontrollably while being restrained. He started to experience the episodes in 2009.

“In the night, he was tearing up the flooring, he took a knife to the office door,” recalls his mother, Mary Nelson.

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