Summary: <p>Profound sadness and unanswered questions mark reactions to Monday's deadly explosions near the finish of the Boston Marathon. Three people died and dozens more were critically wounded. The FBI and Boston police are appealing to the public to share any and all images and recollections which could be helpful in the investigation. Some clues have emerged, but experts warn breakthroughs in the case may be hard to come by. Meanwhile security procedures in public places around the country are being reviewed. Please join us for an update on the investigation and a discussion on assessing risk and summoning resilience in the face of trauma.</p>
