A police operation turned deadly Sunday morning in Montreal, when a handcuffed man went into cardiac arrest.

The incident occurred at about 5:15 a.m. when the 53-year-old man crossed on a red light on Sherbrooke St. at the corner of Bossuet St. in the Mercier-Hochelaga-Maisonneuve borough.

Montreal police officers stepped in and discovered the man was highly intoxicated. Police say he refused to cooperate. The officers put him in handcuffs, and that's when he collapsed.

As is usual following the death of someone in the custody of a police department, another force has been asked to investigate: the Sureté du Quebec.

"This person was heavily intoxicated, and when they proceeded to handcuff this person, this person fell into cardiac arrest," said SQ spokesperson Claude Denis.

Police were not able to resuscitate him and he was confirmed dead in hospital.