(CNN) - Two police officers were among four people killed in a shooting in Fredericton, New Brunswick, police in the Canadian provincial capital said Friday.
A suspect is in custody, and the crime scene has been "contained," police said. The investigation is ongoing and the suspect is being treated for serious injuries.
Police later said there was "no further threat to the public" and no need for any lockdowns.
At a press conference Friday afternoon, Fredericton Police Chief Leanne Fitch identified the fallen officers as 45-year-old Lawrence Robert Costello and 43-year-old Sara Burns.
Costello leaves behind his partner and four children, Fitch said, while Burns leaves behind her husband and three children.
Police have not identified the two civilian casualties, but said they were an adult male and female.
Fitch said that the Royal Canadian Mounted Police are "taking on" the homicide investigation, and that she had reached out to the Serious Incident Response Team -- an independent body in Nova Scotia that investigates police actions -- to look into the "police officer-related shooting aspect of the investigation."
The officers were responding to a call of shots fired at an apartment building shortly after 7 a.m., Fredericton Deputy Police Chief Martin Gaudet said.
After Costello and Burns were shot, additional Fredericton officers responded and engaged the suspect, Gaudet said.
The officers fired their weapons, and about 9:30 a.m. they entered an apartment and arrested the 48-year-old suspect, who has not been identified, Gaudet said.
Officials did not provide additional details about the report of shots fired that initially prompted the police response.
"Our thoughts and prayers are now with the families, friends and colleagues of the two brave Police officers who gave their lives in order to protect and serve and with the families of the other two victims of this senseless act of violence," said a tweet from the city of Fredericton on behalf of Mayor Mike O'Brien, the City Council and other municipal employees.
A spokeswoman for Dr. Everett Chalmers Regional Hospital said it was treating multiple victims from the shooting.
First responders praised
CNN network partner CTV said its reporter there said "police appeared to be focused on one particular residence" and that he heard four shots during a five-minute stretch.
"There is a police officer standing outside with a gun," CTV Atlantic's Nick Moore said on CTV's "Your Morning."
CTV said Moore reported that "police escorted people from their homes" after announcing a suspect was in custody.
New Brunswick Premier Brian Gallant said in a statement that "we are all shocked and saddened to learn this morning of the ongoing tragic incident."
"During this difficult time, our thoughts are also with the courageous women and men on the front lines working to keep us safe," he said.
Prime Minister Justin Trudeau offered his condolences to those affected by the shooting and praised the actions of first responders.
"This morning, first responders rushed to the scene of danger. They did not think twice about what they had to do to keep their fellow Canadians safe," Trudeau's statement said. "They were unflinching in their duty."
"We will not forget the two fallen police officers whose sacrifice no doubt saved lives and prevent even greater tragedy," it said.
Official: Canada takes gun violence 'very seriously'
Many facts surrounding the incident remain unknown, and the investigation is in its early stages, said Ralph Goodale, Canada's minister of public safety and emergency preparedness.
"What we do know is that four Canadians are dead, and that is a huge tragedy for the whole country, and all Canadians I'm sure would want to extend their condolences and their sympathies to the families and to all those who suffered in this incredible loss, including two police officers," he told reporters.
Four years ago, three officers died and two others were wounded in a shooting in the New Brunswick city of Moncton.
Growing gun violence in recent years has been an issue in Toronto, Canada's most populous city. A shooting rampage just last month in that city left two people dead.
Days afterward, the Toronto City Council voted to push the Canadian government to ban the sale of handguns and also for the provincial government to ban handgun ammunition sales within the city.
Asked whether Friday's incident signaled a need for new initiatives to combat gun violence, Goodale said he couldn't comment directly on the day's events but that the Canadian government took the issue "very seriously."
He pointed to legislation meant to increase background checks, improve the license verification process and keep updated records, and to investments in programs meant help the federal government work with provincial governments to deal with guns and drugs.
"Canada is a safe and secure country," Goodale said. "In fact, most crime rates are going down and have been going down for several decades, but the incidents of violence with firearms have been going up over the course of the last five years, and our initiatives are aimed specifically at that objective."
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