NEW : John Lennon checks in with his wife , who has joined the Beatles in the Bahamas . NEW : Canada 's prime minister laments an ` ` inspiring event marred by senseless violence '' Police from Miami to Los Angeles on heightened alert ; off - duty Boston cops called in . London police say they are reviewing security for the city 's marathon on Sunday .
NEW : John Kerry checks in with his daughter , who has run the marathon in the past . NEW : Canada 's prime minister laments an `` inspiring event clouded by senseless violence '' Police from Miami to Los Angeles on heightened alert ; off-duty Boston cops called in . London police say they are reviewing security for the city 's marathon on Sunday .