Army Special Forces Lt. Col. David Diamond felt triumphant. He had just broken his personal record, completing the 2013 Boston Marathon in under four hours, with a few minutes to spare.
After crossing the finish line, in the stretch of road before runners exit the course and join their friends and family, he sat down on a curb to catch his breath and check his phone.
Suddenly, a blast. Diamond knew exactly what it was. He had served five tours in Iraq, and it sounded just like when his convoy hit a roadside bomb in 2003, severely injuring one of his teammates.