A Canadian man has been identified as the lone suspect in a mass shooting at a Quebec City mosque, where six were killed and five others critically injured during evening prayers on Sunday.

Alexandre Bissonnette, 27, is charged with six counts of first-degree murder and 5 counts of attempted murder. In an afternoon press conference, an RCMP spokesperson said that additional terrorism-related charges may be forthcoming.

Bissonnette was arrested along with one other individual following a shooting at the Islamic Cultural Centre of Quebec shortly before 8 p.m. Sunday, in the Sainte-Foy neighbourhood. The second person is being treated as a witness, according to Surete du Quebec.

The Department of National Defense confirms that Alexandre Bissonnette was a cadet between 2002 and 2004 in the Quebec City area. He was an air force cadet briefly in 2002, then an army cadet. Cadets are not members of the Canadian Armed Forces and they do not receive military training.

Laval University, a French-language public university in Quebec City, has confirmed that Bissonnette was a student at the institution’s Faculty of Social Sciences.

Six people were killed in the mosque shooting, including a professor and a grocery store owner.

Five victims were taken to hospital in critical condition. Police say the victims were all men between the ages of 39 and 60. More than a dozen others suffered minor injuries.

Of the five victims taken to hospital, three remained in intensive care Monday morning. The other two were in critical but stable condition, a hospital spokesperson said.

Investigators are asking for members of the public to come forward with any information that might help with the case.

Patrick Lalonde, assistant director of the Service de Police de la ville de Montreal, says security has been increased around mosques in the area. “We have asked for all our police officers to increase the levels of vigilance and surveillance around mosques and other community services,” he said at a news conference Monday morning.

Prime Minister Justin Trudeau and Quebec Premier Philippe Couillard both condemned the incident as a terrorist attack.

“It is heart-wrenching to see such senseless violence,” Trudeau said in a statement. He also offered his sympathies to the victims and his support to Canada’s Muslim community. “Diversity is our strength, and religious tolerance is a value that we, as Canadians, hold dear,” he said. “Muslim-Canadians are an important part of our national fabric, and these senseless acts have no place in our communities, cities and country.”

Trudeau repeated his condemnation of the attack in the House of Commons Monday afternoon, where he again called it a “terrorist attack.” He is slated to visit Quebec City later in the day, along with Rona Ambrose, interim leader of the Conservative Party, and Thomas Mulcair, leader of the NDP.

“We must stand united,” Trudeau said. “Senseless violence has no place in Canadian society.”

Premier Couillard urged Quebecers to stand in solidarity with the Muslim community. “Let us unite against violence,” he tweeted in French.

“This is your home, you’re welcome here,” Couillard said at a news conference, speaking to the Muslim community. “We are all Quebecers.”

Public Safety Minister Ralph Goodale later told reporters that the motivation for the attack is not known, but that it meets the “broad definition” of a terror attack.

He said Canada’s terrorism threat level remains at medium, where it has stood since October 2014.

Quebec City Mayor Regis Labeaume said the city is in mourning. “We have the impression we are dreaming,” Labeaume said at a news conference Sunday night. “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.”

Video from the scene shows several police cars outside the mosque on Sunday night.

Vigils are planned at mosques in several parts of the country, including Quebec City and Montreal.

Members of the Muslim community have condemned the attack, with many calling for tighter security around other mosques in the country.

“We are horrified by this despicable act of violence,” Ihsaan Gardee, executive director of the National Council of Canadian Muslims, said in a statement. “This act of wanton murder must be punished to the fullest extent of the law.”