My heart goes out to those affected by this tragic event: the victims, and their families too, the security personnel, the people in the store at the time. My questions are: why didn't the boy's friends, parents, teachers and psychiatrist realise what he had in mind? If the report is correct that he was telling his friends online about the weapon he had, and they knew he suffering from paranoid delusions, they could have reacted too. More decisive preventive measures could have been taken, on several fronts. The challenge Siam Paragon and similar stores face now is how to screen incoming customers more effectively. Not an easy task to pick out a young teenager as an imminent assassin, unless he looks or acts as if he's crazy right from the start. If this boy was also adept at deception, at hiding his intentions, perhaps nothing could have stopped him doing what he did. As to whether this means tourists & customers should stay away from the stores, they can hold in mind, that statistically speaking, crossing a road or riding a motorbike are far more dangerous activities than shopping.