An Elkhorn man has been charged with sexually assaulting children and taking video of it.

Joseph Mark, 44, is being held without bail after being charged with five counts of first-degree sexual assault of a child, six counts of manufacturing child pornography and one count of intruding on a person without consent.

After searching Mark’s computer, police say they found 367 pornographic pictures and 127 videos taken of a 15-year-old girl being sexually assaulted by Mark over a period of three years, according to court documents.

The documents also allege that Mark videotaped two 15-year-olds having sex and forced a 15-year-old and a 13-year-old to perform oral sex on each other while Mark watched and masturbated.

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Police also found video and photos of Mark sexually assaulting an 11-year-old, court documents said.

Mark also has another case pending in Douglas County District Court in which he has been charged with two counts of first-degree sexual assault of a child and one count of child abuse. He has pleaded not guilty in that case.

According to court documents in that case, a 15-year-old told police that Mark penetrated her with his finger and penis and made her perform oral sex on him. When interviewed by police, Mark denied the allegations.

Mark is due back in court next month on both cases.