the martin family of eight-year-old martin richard , the youngest victim to lose his life in 2013 attack , headed to boylston street to help officials unveil commemorative banners .
four orange signs each bearing a white heart and the word ` boston ' placed at the site .
they were mounted on poles wrapped in blue and yellow flowers , the marathon 's colors , to mark the tragedy that took three lives and left more than 260 others injured .