A disturbing video of a confrontation between students outside an Edmonton school is putting anti-bullying advocates on edge.

"I'm just horrified to see a group of girls mobbing this child," said Linda Crockett, president of Alberta Bullying Research, Resources and Recovery. "It's mortifying because I'm seeing that one girl is laughing hysterically, thinking it's a joke, while this other girl is clearly terrified."

The short video, posted to Instagram Sunday, shows four young women involved in a heated altercation. One girl is backed into a corner, while she is punched and slapped repeatedly in the face. At one point, her head is smashed forcefully into the cement wall behind her. A fourth girl stands nearby and laughs.

"This is absolutely bullying and it's assault," said Crockett. "It's called mobbing when two or more people go after someone. These guys have got together and they're taking her down. She doesn't have a chance."

Crockett said she fears the video, which has garnered more than 78,000 views online, will incite more violence in Alberta schools and make the incident more traumatic for the victim.

She noted other videos of school yard violence have gone viral, and the phenomenon can encourage bullies, desperate for attention, to act out against their peers.

"This could cause some hysteria. This girl could face more teasing, more assaults, because other friends might want to join in. I worry about what this is going to do to that girl," Crockett said in an interview with CBC Radio's Edmonton AM.

"It's out of control. How can that person feel safe again, knowing that it's open for anybody to either laugh at, make fun of, or copy."

Edmonton police are investigating the attack, which occurred in the Riverbend area. But they have provided few details on the case.

Edmonton Public Schools spokesperson Brad Stromberg confirmed the altercation involved students from a public school, but outside of school hours on a day when schools were closed. School officials have declined to provide further information, citing the ongoing police investigation.

"We are always concerned for the safety of our students — regardless of whether or not it's a school day," reads a statement emailed to CBC News by Stromberg. "As Edmonton Police Service is involved, Edmonton Public Schools isn't able to contribute to any public conversation surrounding the incident."

Edmonton Public Schools has a strict no-bullying policy, even when incidents occur off of school property. According to their policy, students can face suspension or expulsion for any number of actions that threaten student safety, including assault.

Crockett said she hopes the perpetrators are punished by both school and law enforcement officials so that the incident can serve as a cautionary tale for other students.

"You do have copycats. Of course, it's going to have far worse effects if it's online," said Crockett. "Hopefully, if they get some counseling for this child, which I hope they do, they'll be able to put it behind them but it's going to be a long process."

CBC News has contacted the girl and her family, but they have not responded to requests for an interview.