Saint Mary's University says it will conduct a special review to find out why student leaders were chanting about non-consensual underage sex in a video captured during frosh week at the Halifax school.

St. Mary's president Colin Dodds said the behaviour of the students is inexcusable.

In a video posted online, the students used the word "young" as an acronym in a chant that included the lines: "Y is for your sister […] U is for underage, N is for no consent […] Saint Mary’s boys we like them young."

Dodds said in a statement: "My colleagues and I were shocked by this incident and are deeply sorry that our students, and now the community at large, were exposed to disturbing sexually charged material."

Dodds said he is forming a presidential council to investigate the incident and ways to prevent any other situations.

Meanwhile, the video drew harsh criticism Thursday from university students and health advocates.

Jared Perry, chair of Students Nova Scotia, stepped down from his position in light of the controversy. Perry is also the president of the student council at Saint Mary's.

"There is not, and has never been, any place for this sort of culture on our university campuses," said Jonathan Williams, executive director of Students Nova Scotia. "While the SMU students involved surely failed to grasp the severity of what they were doing and saying, this very fact highlights the need to speak out about sexism when we see it."

In a release, the student organization said Nova Scotia has the highest rate of sexual assault in Canada.

Just last week, student unions in the province announced that they will research sexual assault prevention and alcohol consumption.

"We are committed to ensuring nothing like what has emerged in the last 24 hours ever takes place again in a Nova Scotia student union activity," said Williams.

The Avalon Sexual Assault Centre, based in Halifax, also spoke out against the chant.

"The message of that chant reinforces rape culture in our society," said executive director Irene Smith, in a release.

Smith said it's particularly disturbing since the video was recorded months after the high-profile case of Nova Scotia teen Rehtaeh Parsons made headlines around the world. Parsons died after an attempt to take her own life. Her family said the teen was the victim of a sexual assault.

The centre said it has received calls from victims of sexual violence who are shaken by the video's content.

Premier Darrell Dexter suggested the students who participated in the chant might be from out of province and don't understand how sensitive the topic of rape is in Nova Scotia.

"Kids, they often act, you know, without considering necessarily the consequences of the things that they're saying. It was very disturbing. I also felt bad for them as well because I think if they had sat for a second and thought about it they wouldn't have engaged in that kind of behaviour," he said.

Students' union apologizes

Perry, who remains in his role as president of the Saint Mary's University Students' Association, said the people who participated in the chant are shocked and disappointed by their own behaviour.

"These are great leaders," said Perry. "This was simply a moment with a lack of judgment."

"I definitely agree that’s not appropriate," he told CBC’s Information Morning. "It’s not tasteful, and I sincerely apologize to everyone who has been offended."

Perry said events set for Wednesday night at the school were cancelled as staff met with orientation leaders.

"A lot of them showed a ton of remorse for their actions. Many of them ended up crying, speechless, jaw drops, and they’re very disappointed by their actions. It’s one of those things that you don’t realize until after the fact."

Outrage after video goes viral

The 15-second video, which was posted on Instagram, has been taken down. But reports on the cheer have been viewed thousands of times.

"People are mad. People are upset. People are angry," said Steve Proctor, a communications manager for Saint Mary’s University. "People don’t understand how it could happen. That’s the reaction shared by the administration."

Proctor said senior administrators who have been on the football field in the last few years have never heard the cheer.

"As you can hear in the clip, you can't even tell what they're saying," he said. "If we had heard the cheer, action would've been taken immediately, as it was in this case."

"I really believe… nobody who was actually doing the cheer believed in what it was."

Still, some students said they weren’t bothered by the cheer.

"We thought it was funny," said Siobhan Evans. "We were all just excited … I don’t regret it."

"It wasn't a big deal to me. I’m not a feminist kind of person. It didn’t affect me personally," said second-year psychology student Amanda Fougere.

All of the 80 frosh week leaders and the entire Saint Mary’s University students' union executive have been ordered to take sensitivity training. The executive will also attend a conference about sexual violence and consent.

"I hope that people will look at how we react to this and how we move forward," said Perry. "This is a huge learning experience for myself, my executive team, and all the orientation week leaders. Hopefully we’ll be able to implement some sustainable practices that will help tackle this."

Proctor said the school will use this as a teachable moment.

"This is a problem, this is a concern that stretches not only across the province, but across the country."