John Prno has resigned as the Region of Waterloo’s emergency services chief.

Prno had been the head of EMS in Waterloo Region since the region took over responsibility for ambulances in 2000.

Prior to that, he was the operations manager of the Kitchener-Waterloo Regional Ambulance Service.

Dr. Liana Nolan, the region's health commissioner, says Prno unexpectedly tendered his resignation last Friday.

“On Friday, John Prno advised us that he was resigning,” she told CTV.

“It was a surprise, that’s really all I can say.”

Nolan, who is now the acting director of Waterloo Region’s EMS division, says Toronto EMS services are available to provide EMS management support in Prno's absence.

Nolan would not say specifically why Prno walked away from his job and annual salary of $150,000, but says she is investigating certain operational matters.

“There have been some challenges that have been brought to my attention about the service, and so we are in the process of looking into them and at an appropriate time I will be making a report to council on that,” she said.

Prno tells CTV he can’t discuss the details of his resignation for legal reasons.

A graduate of Conestoga College, Prno has worked in the ambulance care field since 1975.