Canadian officials have arrested and charged two teenage girls with second-degree murder after they beat a fellow student to death and posted a video of the attack on Facebook Live. 19-year-old Serena McKay was found dead on April 23.

The two girls — whose identities remain unknown — are students at Sagkeeng Anicinabe High School. The video they posted of the terrifying attack remained online for almost four hours before it was taken down. 

Although there is no known motive for the attack, Claude Guimond — Principal of Sagkeeng Anicinab High — believes drugs may have played a role.

"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 CBC News. 

During the gruesome attack, McKay reportedly cried out to the 16 and 17-year-old suspects.

“I'm so sorry,” McKay repeated.

McKay was set to graduate this year and her classmates were absolutely shocked to hear of her death.

Classmates expressed disbelief at McKay's death during a healing ceremony at the school Tuesday morning, Guimond said.

"They were shocked to the core that this could actually happen, that they interacted with these students on a daily basis and they couldn't believe that there could be something as horrific as this," Guimond added.