If you see blue lights tonight, it's to honour officers killed in New Brunswick

Niagara Regional Police asking local residents to consider shining a blue light on their porch tonight to honour two police officers killed in New Brunswick.

Police calling today's events "a terrible tragedy".

Four people were shot and killed and an unknown number of others wounded this morning in a residential neighbourhood on the north side of Fredericton.
  
Two city police officers are among the dead.

One person is in custody, and is being treated in hospital for serious injuries.

A large group of police officers gathered outside the Chalmers hospital this afternoon and watched as the hospital's New Brunswick and Canadian flags were lowered to half-mast.
    
The city's police chief and mayor are planning to hold a news conference this afternoon.