It began with a request by RCMP in Moncton for people in the city to leave their porch lights on at night to aid them in the search for a killer.
People in Moncton responded.
And and so did people across Canada and beyond, leaving their lights on and tweeting photos of them to show their support for the Moncton RCMP as they sought the man accused of gunning down three of their colleagues on Wednesday night.
At a news conference Friday to announce the capture of Justin Bourque, Supt. Marlene Snowman thanked "citizens who were sharing important information via social media."
"It was dark at night time, and those lights that you put on helped our members execute the arrest and locate this individual."
Douglas Mullin of Fredericton put together dozens of the porch light tweets as the campaign unfolded and put them together in Storify form.