Police in Ottawa on Thursday said a 19-year-old man has been arrested following the deaths of two adults and four children at a house in the southern part of the Canadian capital in what authorities called a "tragic and complex investigation." 

Febrio Dezoysa, 19, was charged with six counts of first-degree murder and one count of attempted murder, Ottawa Police said in a statement Thursday. The suspect is a Sri Lankan national who is believed to be in Canada as a student.  

Ottawa Police Chief Eric Stubbs said Thursday that investigators found an edged weapon that was allegedly used in the killings.

"To be clear, this was a mass killing, not a mass shooting," Stubbs said.

Police have identified one of the adult victims as 35-year-old Darshani Banbaranayake Gama Walwwe Darshani Dilanthika Ekanyake. Her husband was also injured and is hospitalized in stable condition.

The couple's four children — ranging in age from 2 months old to 7 years old — were also found dead, police said. Another man, Amarakoonmubiayansela Ge Gamini Amarakoon, 40, was also killed. 

"I want to emphasize this was a senseless act of violence perpetrated on purely innocent people," Stubbs said.

Sri Lanka's high commission in Ottawa said the victims were a family of Sri Lankan nationals. The high commission said that it is in touch with relatives in the country's capital of Colombo. When contacted by CBS News after the suspect was identified, the high commission said that police are investigating the incident and they have nothing to share with media at this moment.

Police were called to the home in the Barrhaven area at around 11 p.m. Wednesday night. A suspect was arrested quickly after that, and police said there was "no continued threat to public safety."

Stubbs told local radio stations earlier that police do not believe the deaths were the result of domestic or intimate partner violence, but that they're also still trying to determine the relationship between the suspect and the victims.

Stubbs said it was a "very tragic scene."

Don Perera, a neighbor, said he met the family that lived in the home last fall at a Halloween party at the nearby Catholic elementary school. He said the father was from Sri Lanka.

Shanti Ramesh, who lives across the street, was alerted to a commotion late Wednesday. From her balcony, she saw a man sitting on the driveway of the home and yelling before two police officers arrived and carried him away.

On Thursday morning, five marked police cars were parked on the street and in driveways near the home, which is a middle unit of a row of brick townhouses.

Several people in white jumpsuits were going in and out of the home throughout the early morning, while parents and kids walked and biked by on their way to a nearby elementary school.

Ottawa Mayor Mark Sutcliffe called the incident "one of the most shocking incidents of violence in our city's history."

"I was devastated to learn of the multiple homicide in Barrhaven, one of the most shocking incidents of violence in our city's history," Sutcliffe said in a post on social media. "We are proud to live in a safe community but this news is distressing to all Ottawa residents."

Investigators said they are seek any surveillance, doorbell or dashcam footage from residents, visitors and businesses who may have been in the area at the time of the incident. 

The homicide investigation comes just weeks after a man was arrested in Canada after the bodies of three children and two women were found dead in different locations.

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• Murder
• Canada