Six men are dead, 17 are injured, and one man faces multiple murder charges following a terrorist attack at a decades-old mosque in Quebec City.

The attack happened at 7:45 p.m. Sunday as evening prayers came to an end at the Quebec Islamic Cultural Centre.

Witnesses said two gunmen burst into the building and opened fire, targeting men on the ground floor.

But despite those eyewitness reports, it appears that only one man actually entered the building and opened fire.

It seems that women and children on the second floor escaped the spray of bullets. Thirty-nine people were unharmed.

The worst hurt were taken to the trauma centre at Enfant-Jesus, while ambulances took those with lesser injuries to St. Francois d'Assise and the CHUL.

Early Monday the CHU Quebec, which runs the hospitals, said that five people were still in critical condition, and that 12 others had been treated for minor injuries and released overnight.

Hospital spokespeople could not specify the nature of the injuries, but said those most seriously hurt had been operated on throughout the night.

As of 7:30 a.m. three were in critical condition, while two were in stable but critical condition in the Intensive Care Unit.

All of those injured were between 35 and 70 years old, while those killed were from 39 to 60 years old.

The mosque issued a Facebook statement early Monday after it was confirmed that six people had died.

"All our thoughts are with the children who have to be told their father has died," said the Quebec Islamic Cultural Centre.

"May Allah give them patience and strength."

The Sureté du Quebec set up a special phone line for relatives wanting information. Public Security Minister Martin Coiteux said they can call police at 1-800-659-4264.

Police said they have also reached out to the Muslim community in Quebec City to offer support and security, and are posting officers outside mosques during prayers.

Swift arrests

Police arrested two men within half an hour of the attack on Sunday evening.

One was arrested near the mosque in the Quatre Bourgeois neighbourhood while the second individual called police to turn himself in.

"Around 8:10 the second suspect called police and told us of his act. He seemed to want to co-operate," said Inspect Denis Turcotte of the Quebec City police force.

"He parked his car [near the bridge to Ile d'Orleans] and an officer arrested him."

Police said reports of a second or third shooter appear to be unfounded.

At noon on Monday, the Sureté du Quebec said one of those two men was a suspect, while the other was a witness.

Overnight, police closed multiple streets near the mosque and officers searched the neighbourhood for clues.

Sniffer dogs patrolled through the residential neighbourhood around the mosque, but the majority of the police presence departed by midday.

Early Monday morning the Sureté du Quebec tactical squad raided a home on Quatre Bourgeois Rd., about one kilometre from the mosque.

Around 8:40 a.m. police left the house with two people and took them away.

There were multiple rumours and hoaxes being spread about the identity of the gunman or gunmen, but police were being very tight-lipped.

"We are not going to talk about their ethnic origins or anything else," said RCMP superintendant Martin Plante.

Police would only say the men arrested were their late twenties and early thirties, and that they did not have any criminal record.

The suspect Alexandre Bissonnette, 27, a Université Laval student, was later charged with the attack. Appearing in court Monday, he faces six charges of first-degree murder and five charges of attempted murder.

The rector and a vice-rector of Université Laval spoke out Monday morning to condemn the attacks, as Bissonnette was a student there.

SQ spokeswoman Christine Coulombe said a joint terrorism task force that included members of the SQ, the RCMP, and Montreal police was dispatched to Quebec City overnight.

"For the moment, nothing leads us to believe there are other suspects linked to the event, but you'll understand we're not taking any chances and we're making the necessary verifications to make sure there aren't any," Coulombe said.

Police will also go through surveillance video from the mosque, which has been targeted before.

Last summer a pig's head, wrapped in plastic and with a note reading "Bonne Appetit" was left in front of the building.

The mosque's leaders said they have been subject to other harassment, vandalism, and other minor threats.

Political support for victims

Prime Minister Justin Trudeau and Premier Philippe Couillard both called the shooting a "terrorist attack."

Couillard ordered the National Assembly to lower flags to half-mast.

"This is a murderous act perpetrated against a specific community and with considerable means," he said. "You can't play around with semantics here."

"We have these devils in our society, like other societies have as well, and we need to recognize that and fight them," said Couillard.

The premier said it was a sign that Quebecers cannot try to isolate themselves from the world.

"Horror exists here too. And violence exists here too. We were hoping that because of the fact that we have such an open and peaceful society that we would be immune to the violence we see around the world but obviously this is not the case," said Couillard.

He added that Muslims in Quebec should not feel alone.

"We must continue to build a society together that is open, welcoming and peaceful. We will do it because we have the energy to do it and the will to do it."

Trudeau issued a statement Sunday to denounce the killings.

"We condemn this terrorist attack on Muslims in a centre of worship and refuge," he said.

"On behalf of all Canadians, Sophie and I offer our deepest condolences to the family and friends of all those who have died, and we wish a speedy recovery to those who have been injured."

Quebec City Mayor Regis Labeaume appeared broken by the terrorist attack.

In a city that normally sees two or three murders each year, having six people killed in one stroke was devastating.

"Quebec City, this magnificent city, is in mourning. I have often said in recent weeks that, despite the peace we have here, we are not immune (to attacks). Well, this has just proven that," said Labeaume.