At least four people, including two city police officers, died in a shooting in Fredericton on Friday morning, the capital of New Brunswick, police reported. A mass shooting in Toronto in July killed two and injured 13.
The incident in the town of Fredericton is said to be "ongoing".
New Brunswick had only three homicide shootings in 2016, according to Statistics Canada.
They're also asking people to refrain from calling the police station because of the high volume of calls. Nearby facilities were closed and authorities told residents to stay locked in their homes.
In Moncton, the province's largest city, a 24-year-old man shot five officers from the Royal Canadian Mounted Police in 2014, killing three and severely injuring two.
He said that police have been searching the complex floor-by-floor.
Fredericton resident Robert DiDiodata said he heard a series of "firecracker" sounds around 7am (8pm AEST).
David MacCoubrey says he awoke in his apartment on Brookside Drive around 7:07 a.m.
"It was sort of like a pop, pop, pop, pop".
Prime Minister Justin Trudeau called the news "awful" and said the federal government is "following the situation closely".
Police have since confirmed "there is no further threat to the public", and said lockdowns were no longer required.
"My heart goes out to everyone affected by this morning's shooting".