A robbery suspect was killed during an altercation with three citizens who stopped him from fleeing the scene of a holdup, Montreal police said Wednesday.

The 34-year-old victim is the suspect in the robbery of a convenience store in the borough of Mercier–Hochelaga-Maisonneuve, Const. Raphaël Bergeron said. His death is being treated as a homicide.

The man was fleeing with cash when three men stopped him late Tuesday evening, he said.

The robbery suspect's uncle, Martin Monette, identified him as Jaeson Perron.

Perron has an extensive criminal record dating back to 2004, including charges of theft and breaking and entering.

Police originally described the incident as an armed robbery, but Bergeron has since said investigators are still working to determine if the man had a weapon when he demanded money.

Police arrived at the scene after a 911 caller reported a fight on Nicolet Street near Ontario Street East at at 8:45 p.m.

The convenience store where the armed robbery allegedly took place is on on Nicolet Street in Montreal. (Lauren McCallum/CBC)

When officers arrived, they located a group of people restraining the man in an alleyway. The man was unconscious, Bergeron said.

He was transported to hospital in critical condition, where he later died from his injuries.

Police say the exact nature of the victim's injuries have yet to be determined, but it appears that no weapon was used. An autopsy will be carried out.

The three men, aged 37, 48 and 78, are now considered "important witnesses," Bergeron said.

They were questioned by investigators and were released Wednesday afternoon without charge.

Police will determine if one or all three will become suspects in the case after they are questioned.

"It is considered a homicide due to the circumstances surrounding the event," said Bergeron, recommending people call police rather than intervening themselves in cases like this.

This is the city's 28th homicide of 2018. There were 24 in all of 2017.