Ask HN: What can we do against terrorist attacks, like the one in Paris?

Hi, I live in paris, and I've been profoundly hit by the violence of tonight's attacks in Paris ( http://www.nytimes.com/2015/11/14/world/europe/paris-shooting-attacks.html ) I think that as technology makers, we have a power to change the world. So my question is simple : What can we do to prevent these awful acts ?

Thanks. (I trust that the HN community is wise enough to discuss about this matter without violence, racism, etc..)