The twisted mind of the perpetrator of the attack on Boston's marathon is impossible to fathom. No matter what their grievance or message, who could believe that harming children, fun-runners, athletes and spectators was an accomplishment? Yet the bombs were timed to cause the maximum loss of life, without regard for who was caught in the blasts, all in the name of making a point for which none of us will now ever care. There will never be sympathy for people who commit such acts, no matter how justified they may seem to themselves; there will only be unity against their extreme ways.

That is especially so given the event that was targeted, those who were caught up in the attack and the manner in which it was carried out. The Boston Marathon is among the world's most prestigious, its 117-year pedigree ensuring that runners from far and wide and all walks of life want to participate. Dozens from China, including Hong Kong, were among the 23,000 participants, their thoughts on best times, goals, raising funds for worthy causes and simply having fun. The half a million spectators who lined the historic 42-kilometre course, friends, relatives, tourists and the curious among them, were celebrating the occasion, a monument to athleticism, accomplishment and enjoyment.

But four hours into the run, long after the winners had broken the tape, two explosive devices went off seconds apart near the finish line. There is no busier place or time during a marathon, with a majority on the course and spectators packed tightly to cheer on and celebrate. For the cold-hearted and calculating, it was the perfect setting. There was a ball of fire, a boom and then chaos, the cheers and applause in an instant turning to wails and screams.