Leejay Levene went to a Waterloo, Canada dental surgeon to have three wisdom teeth pulled.

While his mother settled into the waiting room, the Waterloo teen sat back in the dentist’s chair and slipped under a general anesthetic.

Then something went so wrong that he was left struggling for breath. Soon, a call was going out to 911, and the anesthesiologist present for the procedure was trying to resuscitate him.

Paramedics, then doctors at Grand River Hospital tried everything, but by the next evening, the 18-year-old was dead.

Now, the Waterloo Region coroner, assisted by regional police, is trying to determine what happened to the healthy young man, who was undergoing a dental procedure routinely performed on patients his age.

“This is such an anomaly,” Irwin Fefergrad, the registrar for the Royal College of Dental Surgeons of Ontario, said of Levene’s death last Thursday.

“It’s so unusual and rare. We are all in a state of shock and sadness. This is a safe procedure.”

Dr. Timothy Wallace, the oral surgeon performing the extraction, said the tragedy that occurred in his office is “once in a lifetime.”