A vile act like murder committed in rage would be justifiable to find retribution with another murder sanctioned by law as a punitive measure. More than retaliation what is required is to create an environment of understanding to create a bridge for those in darkness so that they can be helped out of their self created hell, which demands a highly persevering wise and matured approach.
When the rudimentary principles of ethics and morality are complemented with compassion and knowledge then the person will never betray his own conscience. But if conscience is absent, then the person has no humanity in him. What is humanity and what makes one humane, all this needs to be taught and learnt in a conducive environment. Only then it is possible to respond and not react and for this a person needs to cultivate introspection, heightened awareness so as to rise above the shortcomings of mind, eradicate weaknesses and work on expanding consciousness.
The complexities of life cannot be addressed with one line resolutions. If we wish to make a better society the let us first become better parents, better teachers and better human beings. Then we share, spread and disseminate this knowledge by example so that other too get a chance to evolve to live compassionately and cordially. If you hate yourself, you can give hatred to other whereas if you love yourself and see your own true self reflected in all, then there is no way you could cause hurt to another.
We as society need to understand that there are going to be all kinds of people with different mindset, inclinations and dispositions and it would be a utopian idea to believe that everybody will become enlightened one day miraculously. Yet a harmonious environment of love, friendship and respect has to be created and every individual needs to endeavour towards making it possible. If we all set an example of an evolved and responsible behaviour, inspire those around us by instilling peace and love and mutual respect, it would certainly make a difference.