@CNN: To commemorate the 5th anniversary of the Boston Marathon terrorist attack, a group of runners used GPS tracking on a 4.5-mile course across the city to spell out “Boston.” This image is from Michael Wardian’s running app, Strava. https://t.co/anth4HNks3 https://t.co/Ze35O9hS4N

@CNN: To commemorate the 5th anniversary of the Boston Marathon terrorist attack, a group of runners used GPS tracking on a 4.5-mile course across the city to spell out “Boston.” This image is from Michael Wardian’s running app, Strava. https://t.co/anth4HNks3 https://t.co/Ze35O9hS4N