Internet horror meme “Slender Man” sends two 12 year old girls off the rails in brutal stabbing of pal in the woods, Wisconsin cops say.

Two Waukesa, Wisconsin preteens Morgan Geyser and Anissa Weier charged with stabbing their 12-year-old friend are sorry for the attack and called it "wrong," police said.

Morgan Geyser and Anissa Weier invited their intended victim to a sleepover. When the three girls played hide-and-go-seek the next morning, cops say that Geyser and Weier attacked.

The girls allegedly stabbed their classmate 19 times in an act of allegiance to Slender Man, a mythic monster meme online.

The girls told cops they saw the character on creepypasta.wikia.com. They planned to kill the girl in a blood ritual and then run away to Slender Man's imaginary mansion in a lush forest.

NBC Chicago reported the two Waukesha 12-year-olds told police that they struggled to decide who would be the one to wield the knife.

But the two handed the knife back and forth while arguing who should stab the girl and who should hold her down, police said.

The victim was in stable condition Monday. Geyser and Weier have been charged with attempted murder.

The two girls were charged as adults with attempted first-degree murder. If convicted, they could face up to 65 years in prison.If the case is moved to a juvenile court, the girls could serve time in a juvenile facility until they are 25 years old.

Both Geyser and Weier are being held on $500,000 bail each.