MILWAUKEE - The parents of one of two Wisconsin girls who were 12 when they allegedly stabbed another girl 19 times to impress the fictional internet character "Slender Man" say they were as shocked as anyone by the 2014 attack.

In an interview Monday with ABC's "Good Morning America," Bill and Kristi Weier, parents of Anissa Weier, say she's remorseful. The couple also says Anissa shouldn't be tried as an adult because they say Wisconsin laws haven't kept up with the science of juvenile brain development.

The interview came ahead of an HBO documentary, "Beware the Slenderman."

Anissa, now 15, and 14-year-old Morgan Geyser have pleaded not guilty in adult court by reason of mental disease to attempted homicide in the 2014 stabbing of classmate Payton Leutner in Waukesha.