Newt's death is the reason that Anthony is such an angry kid, not only he lost the only person who could understand and defend* him, but also he probably had a fall out with his brother and he loses him before he gets the chance to make up with him
*Some of the reasons behind Anthony's anger are the people that are so blinded and hateful that hurt other people without a second thought
That, and also the fact that he just doesn't have control over everything and his solution to cope is to get angry at the situation or how people act
The thought of his brother haunts him every, something that he often rejects and pushes back because he blames himself for it, until he comes to the acceptance that his brother probably forgives him and he should stop blaming himself for everything