HAWKESBURY, Ont. — A former colleague of Brian Nadler, the Ontario doctor arrested this week in connection with suspicious deaths at a hospital, described him as compassionate with patients.

Dr. Ahmed Hanfy trained with Nadler for about nine months at the University of Nevada, Reno, and says he can’t recall any red flags related to Nadler’s behaviour.

Hanfy said in an interview Saturday Nadler had a tendency to argue with other physicians but said the disagreements were confined to medical matters, such as the best course of treatment for a patient.

Nadler, 35, a specialist in internal medicine who worked at the Hawkesbury and District General Hospital in eastern Ontario, remains in custody after he was charged with one count of first-degree murder Friday.

Police said the arrest was made in connection with multiple suspicious deaths at the hospital, but have not specified the number of deaths under scrutiny or offered any details about Nadler’s alleged victim.

Nadler previously practiced in Saskatchewan, where the province’s College of Physicians and Surgeons said he was charged with unprofessional conduct for allegedly using a profane term when referring to a female colleague following an argument in 2014.