Although, police had yet to confirm the student's identity Sunday, it had been confirmed by the medical examiner and by an email the school president sent to students that Collen's body was found Saturday night.
Collen was last seen November 14 with friends at the Alpha Sigma Pi fraternity house on the school's campus. His body was found days later in the same location, reportedly in a storage room. Police were not explaining how that was possible Sunday.
When Collen, who was in ROTC, did not show up for physical training the next day,fellow cadettes tried looking for him. Then, they notified his parents.
Family and friends have said it was unlike Collen to be gone for such a long time.
An autopsy Sundday revealed that he died by asphyxia from inhaling carbon dioxide from a canister. His death was ruled accidental.
Colleen was a biomedical engineering student from Lincolnwood.
In a statement, IIT Pres. John Anderson limited himself to extending his condolences and saying that a memorial service for Collen would be held in the next few days. Detailed plans on the service have not been released.
IIT is making counselors available for students.
Police say their investigation into the case continues.