Tributes have been paid to a Mountie and mother-of-two who was among at least 16 killed after a denture-maker went on a shooting spree across Nova Scotia.

Royal Canadian Mounted Police constable Heidi Stevenson was a 23-year veteran of the police force. In an emotional statement shared on Sunday evening, RCMP assistant commissioner Lee Bergerman wrote about the loss on Facebook.

"Today is a devastating day for Nova Scotia and it will remain etched in the minds of many, for years to come," she wrote.

"What has unfolded overnight and into this morning is incomprehensible and many families are experiencing the loss of a loved one," Bergerman said. "That includes our own RCMP family."

Bergerman confirmed "with tremendous sadness" that Stevenson was killed "while responding to an active shooter incident." It is unclear whether Stevenson was killed by suspect Gabriel Wortman, 51, when he was confronted by police at a gas station in Enfield, Nova Scotia, or if she died during an earlier altercation with the man.

"Heidi answered the call of duty and lost her life while protecting those she served," Bergerman said. "Earlier this afternoon, I met with Heidi's family and there are no words to describe their pain. Two children have lost their mother and a husband his wife. Parents lost their daughter and countless others lost an incredible friend and colleague."