Depends on where you place worth. Some people say life is precious thing, but how precious something is determined by its rarity and with 6 billion people and more joining each and every day that rarity is not readily seen so human life is loses its glitter, but if you take the scope of the universe we may be just one tiny spec of a world in an otherwise dead reality thusly in truth life is really rare.
Okay, I am rambling nonsense. BLAH!
I side with your latter point, up to a point. However, the truly extraordinary thing about life is its potential. Even if some of the guys who get killed were as thuggish and inane as the shooters claim they might still have changed over time. Unfortunately we'll never know now.
I'd like to expand on my previous point. Steve said earlier that government violence legitimised incidents like this. I think that a general post-sixties solipsism and new capitalism. The basic principle is that the customer/individual is usually right, and the collective is wrong. We're encouraged in every single walk of life to behave as we choose, with little regard for others. This has had its positiv side in incraesed poltical activism, but it's also had its negative side. I think this sort of behaviour is one aspect of it.
Or I could be getting all pop psych.