Jackson will act cold and heartless, but it's only to hide the fact that he's on the verge of a mental breakdown. A few years before he joined Thanatos, he was diagnosed with an untreatable brain tumor in his pain centre, causing terrible phantom pains 24/7. Because he knows he can die any moment, he tries to stay at a distance from everyone, so he will leave very little people behind once he dies. Jackson tries to hide his medical condition, and anyone asking about the bittles of pills on his nightstand and in his bag will not be dignified with an awnser.