Editor's Note: (Kelly Wallace is CNN's digital correspondent and editor-at-large covering family, career and life. Read her other columns and follow her reports at CNN Parents and on Twitter.)
(CNN) There is still so much we don't know about how a 13-year-old Blacksburg, Virginia, girl got to know an 18-year-old Virginia Tech freshman before he allegedly stabbed her to death.
What we do know is a bit more about a possible motive in the death of Nicole Lovell, a middle school student. David Eisenhauer, a college track and field athlete, is thought to have had an inappropriate relationship with Lovell and stabbed her to death because she threatened to expose their relationship, according to a law enforcement official.
But how did they meet? How did the alleged relationship begin?
Signs are pointing toward an online network, after police arrested Eisenhauer based on tips and leads obtained from social media. We also know that Lovell was active on social media, including posting in a Facebook group called Teen Dating and Flirting, which has since been shut down.
On New Year's Day, Lovell reportedly posted a selfie in the group, with the comment "cute or nah," which garnered more than 300 responses, most of them in the vicious category. Lovell also was active on the anonymous instant messaging app Kik, according to a neighbor who told The New York Times that Lovell had showed one of her daughters texts she had exchanged with an 18-year-old that she planned to meet the night she disappeared.
I've reported on parents who just aren't aware of Kik and other social applications that their teens might be using, such as Ask.fm, and how the anonymity on these sites can lead to bullying and other dangerous behavior. So what can parents do to keep their kids safe on social media?
On the one hand, especially after a tragedy like the death of Lovell, you can see how they might want to ban their children from all social media. No engaging, no trouble. But that's not a reality in today's world, when social media is a key way teens socialize and spend their time.
Instead of a ban, parents should show interest in their children's online lives, said Diana Graber, co-founder of CyberWise.org, a digital literacy site for parents, educators, teens and tweens. This is not a new piece of advice, but it bears repeating again and again: Be involved.
"This can be as simple as asking your child to show you how to use an app they love, and then let that evolve into a conversation about what's going on in their online world," said Graber, who also teaches "Cyber Civics" to middle schoolers in Aliso Viejo, California.
The conversation and interest should begin the moment your child starts using digital devices, she said.
Parents have been "checking in" for centuries, and they shouldn't believe that just because their kids are in the house behind a screen that something can't go wrong, said Katie Greer, who has provided Internet and technology safety training to schools, law enforcement agencies and community organizations for nearly a decade.
She says parents can be reasonably involved in their children's digital lives by asking questions and doing spot checks, which can highlight potentially dangerous or problematic situations.
While every parent has probably taught their children not to talk to strangers in the offline world, many probably haven't had a conversation about how to make relationships in the online world, said David Ryan Polgar, the co-founder of the Digital Citizenship Summit, which is a global network of conferences focused on improving social media use.
According to a Pew Research Center national survey last summer, nearly six out of 10 teens say they met a new friend online, and 20% of the teens who met people online followed up in person.
"Many physical relationships and friendships are first started online before they move offline. In other words, online, we are constantly talking to strangers," said Polgar, a former attorney and college professor who frequently comments on tech issues. "It is easy to feel a false sense of intimacy through online relationships. It is important to 'trust but verify,' and have a healthy level of caution both in one's interactions online and in the physical realm."
Greer, the national Internet safety expert, said a great way for parents to stay on top of the apps their kids are using is to use the "Ask to Buy" feature with Apple devices or the "Authentication" feature in the Google Play Store.
"Utilizing these features will make it so that parents have to approve apps before they're installed on their kids' devices," Greer said. "This way, parents can gather information on apps before allowing their kids access to them, while staying active and informed on the latest and greatest (or not-so-great) apps."
Graber of CyberWise said there are also online parenting apps, such as PocketGuardian or ThirdParent, that will catch and alert you to unsafe or potentially harmful activity on your child's phone and suggest what to do or where to turn for help.
Developing a family relationship with social media that takes into consideration age, family values and any unique circumstances is vital, and so is communicating how the family is going to monitor social media, Polgar said.
"The goal is to have tech transparency as a family in order for parents to best supervise and mentor their children," he said.
If you are a parent and you are wildly frightened after this latest tragedy, I can relate. Who knows what platforms and apps will be available when my girls, who are 8 and 9, get to middle and high school?
But I keep thinking about the smart advice from these Internet safety experts: We can take steps to try to keep our kids safe. There is a way.
Educating our kids about digital safety, engaging with them on what they are doing and what they are experiencing, and empowering them to be safe in the online world can help give them the "modern street smarts" that are required in today's world, said Polgar.
"Since kids spend more time online than they do in school or with their families, parents can no longer turn a blind eye to their digital activities," said Graber of CyberWise. "The stakes are just too high."
What do you think parents can do to try to keep their kids safe online? Share your thoughts with Kelly Wallace on Twitter @kellywallacetv or CNN Health on Twitter or Facebook.