Two teenagers arrested for murder after posting Facebook Live video where they 'beat student to death'

Serena McKay was brutally assaulted in clip - which was streaming on social media for nearly four hours before it was ordered to be taken down.

Two teenage girls have been arrested on suspicion of murder after a video on was posted on Facebook live of a fellow student being beaten to death.

The unidentified Canadian teenagers, aged 16 and 17, shared the disturbing footage to their social media page as well as a private instant messaging app, according to authorities.

The victim, 19-year-old Serena McKay, was last seen by her family Sunday, April 23, the same day she was found dead nearby the home, reports the New York Daily News.

McKay, who was due to graduate next month, was heard in the recorded video crying out to her perpetrators, “I'm so sorry.”

The footage was left streaming on Facebook for nearly four hours before it was ordered to be taken down, according to a CBC report.

It comes as Facebook has faced criticism for not doing enough to address the issue of brutal crime on the video streaming service.

Principal of Sagkeeng Anicinab High, Claude Guimond alleged drugs may have been a factor in what he described as a "violent assault".

"After seeing what I saw on the video, you know what? There's nobody in their right mind [who] would do something like that, unless they were extremely high on whatever and just totally, like, out of it," Guimond told the newspaper.

The Royal Canadian Mounted Police are currently investigating the incident, as well as "a case of mistaken identity" which involved officers grabbing and handcuffing the wrong 16-year-old suspect at a local bus stop.

"Once it was learned that it was not the correct person, she was released immediately," police said in a statement.

The mistakenly arrested teen’s parents have since filed a formal complaint on the incident.