They're asking members of the public to stay clear of Brookside Drive between Main and Ring Road. It was not immediately clear what caused the shooting. Later, police confirmed four people had been killed in the incident.
Fredericton is located about 50 miles northeast of the US border with Maine.
"With the tempo, it might've been a gunshot", he said.
Area resident Robert DiDiodato told the CBC that he heard sounds like a "firecracker" at around 7am. 'It was sort of like a pop, pop, pop, pop'.
Residents were warned to "stay in their homes with doors locked at this time for their safety" by the police.
About five minutes later, he could hear similar noises near his home.
According to the force's Twitter account, police units responded to an "ongoing incident" on Brookside Drive at around 7:30 a.m.
Police continue to have the Brookside area contained for the foreseeable future as the investigation is ongoing.