WARNING: This story contains disturbing details

TORONTO -- Eight students at a prestigious Toronto private school have been expelled in connection with two disturbing incidents, one of which involved an alleged sexual assault of a teen that was captured on video and has since triggered a criminal investigation.

In an email to parents, St. Michael's College School revealed that after receiving the video of the alleged sexual assault on Monday, it launched an internal investigation that lasted until Wednesday and included interviews with the students involved and their parents.

"Upon completion of its internal investigation, school administration provides information related to the second incident to police, and gives the second video (locker room) to police," says a timeline of events the school released Friday.

St. Michael's also acknowledged Friday that "there have been many questions about our handling of the matter and the sequence of events leading to the expulsion of eight students and one suspension resulting from two" incidents.

Those questions stem from the school's initial statement that it had notified police of both incidents on Monday, which was disputed by police. A spokeswoman for the force said they launched an investigation into the alleged sex assault incident on Wednesday after receiving media inquiries about the video that was circulating online. Sources said it was police that reached out to the school on Wednesday and received a copy of the video.

Hours later, police issued a statement saying investigators from the department's child exploitation section had determined that the video met the definition of child pornography, and that anyone possessing a copy should delete it immediately.

The all-boys Catholic institution that teaches grades 7 through 12 said the administration received a video on Monday morning of the first incident that occurred in the boys washroom, and after conducting an internal investigation it notified police. On Monday evening, the school received a video of a second incident in the locker room. Both events "severely violate the student code of conduct," the school said in the email.

Police and the school have revealed few details about the incidents, but two police sources say the incident that is being criminally investigated -- the "second incident" in the locker room -- involved a group of students on the football team pinning down another student where they allegedly sexually assault him with an object.

Those sources say the first incident in the washroom involved members of the basketball team bullying a student and soaking him with water.

"We understand and share the anger and distress that such horrible acts could happen on our school grounds involving boys in our care," the school said in the email to parents. "It is unacceptable and falls far short of upholding the principles we strive to live by."

The school said four students were expelled and another one was suspended in connection with the washroom incident. It said four others were expelled in connection with the locker room incident.

The school said it notified police on Thursday of a third incident, but provided no other information about it to parents. The school was holding two meetings with parents Friday to discuss the situation.

"As school administrators and educators, we bear a heavy responsibility to help guide our students through a challenging period in their lives -- when external forces are often in conflict with the notion of doing the right thing -- and these incidents were a stark reminder that we have more work to do," the school wrote to parents.

It said crisis counsellors are on site to provide support.

Police said the investigation remains in its early stages and no charges have been laid.

St. Michael's is known for its athletic programs, and alumni include hockey greats Frank Mahovlich, Dave Keon and Tim Horton. Other alumni include Ottawa Senators owner Eugene Melnyk. It is run by the Basilian Fathers with roots dating back to the Congregation of St. Basil in France that is a "fully independent, Catholic high school," according to its website.