Retired FBI agent John Egelhof respects the power of the Internet and harnessed it over his long career. But in the aftermath of a chilling Wisconsin crime — one in which two preteen girls attempted a human sacrifice in tribute to "Slender Man," a make-believe online bogeyman — Egelhof doesn't mince words about the ugly underbelly of this ubiquitous tool of the modern age.

With a mouse click or screen tap, today's younger generations have unprecedented access to the worst of human nature: jihadist beheading videos, or sites that idolize school shooters or recruit young American immigrants to join terrorist organizations back in their homelands, just to name a few. "The Internet is just this black hole that kids can fall into for a variety of reasons,'' said Egelhof, one of the lead investigators of the 2005 Red Lake, Minn., school shooting.

"Kids have a secret world that we don't know about. That secret world is far more sinister than ours when we were young. It's a problem we as a society have to face.''

That the Internet has dark corners is hardly a revelation. But the attempted murder by two 12-year-old suburban Milwaukee girls May 31 offered an electric jolt of a reminder about how little is known about this powerful digital engine's effects on still-maturing minds.

With smartphones now standard operating equipment for teens and preteens, and as educators push to equip even young elementary schoolchildren with iPads for school and home use, it's a serious issue that the nation can't be blasé about. Yet the debate here and elsewhere has largely been about access to tablet computers and whether a technological gap will develop, leaving children in less-well-off school districts at a disadvantage.

While educators are studying the pedagogical role of Internet access, more research on its impact on young people is desperately needed and may be even more important. Until that happens, the push to get tablets into students' hands needs to be accompanied by much stronger discussions about responsible use, parental monitoring and critical-thinking skills that at the very least coach kids about sourcing their information.

The vast majority of kids will handle access just fine or have minor issues. But for a small number of kids who are especially vulnerable, exposure may enable harmful actions.

Egelhof wrote a powerful 2012 Star Tribune commentary pointing out that school shooters often obsessively visit sites about previous tragedies, and a sick sense of competition has emerged to one-up the previous death toll. Boston Marathon bomber Dzhokhar Tsarnaev, who was 19 when he was arrested, told investigators he learned how to build pressure bombs from an Al-Qaida website.

Sometimes websites encourage young people to harm themselves. A 2005 Star Tribune story detailed how pro-anorexia sites encourage cultlike worship of a mythical higher power called "Ana,'' who commands devotion and starvation.

What may be most disturbing about Wisconsin's Slender Man case is that these two girls didn't even come close to visiting the Internet's darkest corners. Arrested and now charged as adults with attempted homicide, the two bespectacled girls told police that they regularly visited a site called "Creepypasta Wiki,'' which is where they learned about Slender Man.

From an adult's perspective, Creepypasta Wiki looks harmless. It's a collection of short, campfire-style scary stories posted by amateur writers. The images of Slender Man — an elongated, faceless man with tentacles for arms — are obviously fake.

But somehow these two girls were so deep into the Slender Man fantasy world that they thought they'd be rewarded in real life for a human sacrifice. On May 31, they took another 12-year-old friend into a wooded area near their Waukesha apartments, allegedly stabbed her multiple times, then went to Wal-Mart, apparently to await Slender Man's invitation to live with him in his forest mansion. Fortunately, their victim survived.

Previous eras recognized the potential danger of new communications technology on still-developing minds. The Hays Code provided strict moral guidelines for filmmaking beginning in 1930, with replacement in 1968 by the motion picture rating system. TV networks also quickly developed "mature content" warnings.

It's difficult to imagine similar restraints that could reliably protect kids and teens from inappropriate or harmful information on the sprawling Internet — or stop them if their Web behavior suggests dangerous obsessions. But it's time to have a serious discussion about how we as a culture can do better.

"Parents and extended families need to take a role and say, 'Why are you watching that stuff, what are you doing with your spare time?' '' Egelhof said. "Our best hope as a free society is having parents stay on top of kids and educate them to know right from wrong.''