Ever see that Far Side cartoon where two scientists were at a blackboard, and one says "Egad, we've done it! We've mathematically proven the true meaning of the universe! God, I love the thrill of scientific discovery." And the math on the board was a huge jumble of complex formulae on the left side, and the right side simply had, in large letters, "= 0."

"It doesn't matter how many lives will be saved, because in the end everyone will die, including the assailant."

Of course, but is this to say that you would not take steps to save anyone's life, since they're just going to die anyway? Why bother with funding fire stations and police departments, when that money can go enrich the lives of the lucky living?