It happened Sunday afternoon inside the police headquarters at 474 Elgin St. Ottawa police Chief Charles Bordeleau notified members of the force in an internal email.
In a media release issued later Sunday, Bordeleau said the force's thoughts and prayers are with the officer's family.
Police are not releasing the officer's name until his family and friends are notified.
"I am saddened to report that a well-respected and well-loved member of our service died this afternoon after an incident at 474 Elgin. The news of his death pains us all," Bordeleau wrote. "Those who have worked with him know him as an excellent example of a hard-working, dedicated officer who loved his job.
"Today we are working to ensure that [his family is] supported. We are also ensuring supports are in place for all of our members and our loved ones."
The province's Special Investigations Unit has invoked its mandate and is handling the investigation.