Criticism and questions are being raised following the death of a tiger at the Assiniboine Park Zoo in Winnipeg.

Animal advocates want an independent investigation done by someone other than the zoo.

In the past three months, three incidents have happened at the Assiniboine Park Zoo.

In July, wolves tried to tunnel into the polar bear enclosure. Last week, polar bears damaged the seal enclosure. On Sept. 25, a tiger went into another tiger enclosure, where it was killed.

The latest incident happened as a Grade 12 biology class from the Lord Selkirk Regional Comprehensive Secondary School looked on.

"The two tigers - they kept sizing each other up and eventually one tackled the other one and pinned him to the ground and that's when he went in for the bite,” said Dierdre Neumann. "We heard a crunch and at first I thought it was just me and then I went and confirmed with my other classmates and they heard it too."

Students said the zoo keeper was trying to distract the tiger by dumping water on them. More zoo keepers arrived and told the classmates to leave the area.

“Some of the students and staff were upset at what they saw. Upon returning to the school, the students and staff were offered the services of the guidance department as a precautionary measure,” said the Lord Selkirk School Division in an email.

The students were also given a newsletter to bring home to their parents.

Now the zoo is investigating what happened.

"The zoo is currently conducting a full review of the incident, and will take all necessary steps to insure a similar incident will not occur," said Margaret Redmond, president of the Assiniboine Park Zoo, on Thursday.

Zoocheck Canada said this could suggest a larger systemic problem at the zoo. "While it seems the death of the tiger may have been due to human error, the incident warrants a full review by an independent third party not connected with the zoo or the zoo industry."

Some visitors said the decision should be left up to the zoo director.

Len Bayback supports the zoo's internal review.

"If he or she feels that they have the proper resources to undertake the review internally, then I’d be fine with them proceeding that way,” said Bayback.

The Assiniboine Park Zoo declined CTV Winnipeg’s request to comment on Friday.