One of the differences between animals and people: animals act on instinct and impulse, with little thought to consequences. The occasional act of altruism or nurturing on the part of animals is always newsworthy because it's so exceptional.
Humans, on the other hand, are capable of more. We can overcome our genes and our emotions and our impulses and act with reason and sense and compassion. We can consider our actions' consequences; we can consider how our actions will affect others.
These terrorists are not, by my definition, humans. They kill innocent people. They kill men, women and children to make a political statement. Or to bring attention to their cause. Or just to cause pain. That's not what people should do.
There can be no negotiation with such inhuman monsters, for to do so only rewards their actions. They must be hunted down and put away for their crimes, prevented from ever hurting another person again.