BOSTON (Reuters) - Even as police prepare for a massive presence at Boston's first marathon since the 2013 bombing attack that killed three people and injured 264, officials acknowledge the sheer scale of the event poses inevitable security risks.
More than 3,500 officers will be stationed along the 26.2 mile (42.2 km) course starting in suburban Hopkinton, Massachusetts, and ending among throngs of spectators at the bars and restaurants of Boylston Street, where two homemade pressure-cooker bombs ripped through the crowd last year.