A second video showing a horrific attack on a young woman linked to a 19-year-old's death in Manitoba's Sagkeeng First Nation surfaced on a public Facebook post for hours Wednesday.

CBC News has seen both a shorter video of the attack and a longer one. The latter clearly shows the victim's face, beaten and bloodied.

The body of 19-year-old Serena McKay was found Sunday night near a home Sagkeeng, a community 100 kilometres northeast of Winnipeg. She had been reported missing earlier that day.

Classmates of McKay's alerted their high school principal, Claude Guimond, on Monday to the online video. After seeing the victim's face, Guimond said he believes it was McKay and that he had forwarded the evidence to the RCMP.

The chief of Manitoba's Sagkeeng First Nation wants the video of a vicious attack on a young woman — some say the same woman later found dead in the community — pulled off Facebook. The body of the woman believed to be the victim in the video, 19-year-old Serena McKay, was found Sunday night near a home in the community 100 kilometres northeast of Winnipeg. 2:19

Sagkeeng Chief Derrick Henderson said the girl's mother is extremely disturbed by the existence of the video, and he is calling on Facebook to delete it.

"I've asked Facebook and I've asked the major crimes unit to get that video removed, whatever it takes," Henderson said. "It's pretty hard once it gets out there, I guess. But there must be some mechanism there available."

The social media company told CBC News it is looking into the matter.

"This was a horrific tragedy, and our hearts go out to the family and friends of Ms. McKay. We have not been able to locate the video on Facebook, and are working with law enforcement as they investigate," said a spokesperson for Facebook.

The longer video, which was available for at least four hours Wednesday, was removed from the site after CBC reported it to Facebook and the RCMP.​

Manitoba RCMP are investigating whether the video is related to McKay's death.

"To me, the video is shocking, that someone can stand there and watch it and not assist," said Sgt. Paul Manaigre.

Two teenage girls, aged 16 and 17, from Sagkeeng have been charged with second-degree murder in McKay's death and are in custody. As minors, neither can be named.

All three teenagers attended the same Sagkeeng Anicinabe High School, although McKay lived in the neighbouring community of Powerview-Pine Falls.

'I'm so sorry,' victim says in graphic video

The longer video of the assault, which was public briefly on Facebook Wednesday, shows a girl's head being stomped on by a heavy boot. It's unclear how many people are around her, but there are at least two females.

A viewer could see the victim's blood and facial injuries and hear the sound of bones cracking during the assault and voices swearing at her.

RCMP have taped off the Sagkeeng home in connection with McKay's killing. (CBC)

During the assault the victim cries out, "I'm so sorry." No context is available as to what she is sorry for or why she is being attacked.

"If you send anyone after me I will kill you. I will f--king kill you myself," a female voice says to the victim.

While the recent video has been removed from Facebook, the graphic material can still be shared on the site through Facebook Messenger, according to RCMP.

A disturbing trend online

Daniel Tobok, chief executive officer of online security company, Cytelligence, said the video is the latest example of a growing, disturbing trend — Facebook users sharing videos of real assaults and killings of people thousands of times.

"It's really up to us as citizens, as subscribers, members you know, when we see something inappropriate it's our duty to report it," said Tobok.

Recently a Thai man broadcast himself killing his 11-month-old daughter on Facebook, and last week a fatal shooting in Cleveland was visible for two hours on the site.

While social media sites currently rely on users to report graphic content, they should design stronger filters to stop this type of content from being uploaded in the future, Tobok said.

"I would just urge them to up their game," he said. "You will never be able to stop it, but you can minimize it."

Posting videos of attacks online is not illegal, said RCMP Sgt. Manaigre, but people who film attacks and do not come to the aid of the victim can be charged with being an accessory.

Manaigre said that because the video is being shared through personal messages police are skeptical about whether Facebook can control or stop the spread of the material.

Sagkeeng Chief Derrick Henderson says Serena McKay's death has devastated the community. (CBC)

'We have to continue and move forward'

Henderson believes the attack and death of McKay could be linked to economic and social problems in Sagkeeng.

"I'm not sure what the circumstances are of what happened, but I know a lot of it can be related to lots of factors like addictions. I know that's an issue in my community," he said.

The chief said the homicide has been devastating to many in the community, but he hopes it sparks changes in Sagkeeng.

​"Even me, as a leader, it's so hard to stomach, but we have to continue and move forward and try to make it a better place for our people."​